The Mentawai Forearc Sliver(MFS)is characterized by oblique deformation formed as slip partitioned between normal and parallel trench plate convergence.The surge of great earthquakes from 2004 to2012 along the adjacen...The Mentawai Forearc Sliver(MFS)is characterized by oblique deformation formed as slip partitioned between normal and parallel trench plate convergence.The surge of great earthquakes from 2004 to2012 along the adjacent Sunda trench left a large unbroken segment known as the Mentawai Seismic Gap.Here,we adopted continuous Global Navigation Satellite System(GNSS)observation data to identify the present regional crustal deformation using geodetic strain rates.The principal strain rate,dilatation rate,and maximum shear strain rate are about 0.13 microstrain/yr,0.2 microstrain/yr,and 0.1 microstrain/yr,respectively,with the range of its uncertainties between 0.01 and 0.04 microstrain/yr.The dilatation and maximum shear strain rates reveal the spatial coverage of strike-slip duplex and backthrust tectonics along the Mentawai Forearc Sliver.展开更多
The Lembang Fault is a major geological feature in West Java that borders the northern edge of Bandung(one of Indonesia’s largest cities).It lies just south of the active Tangkuban Perahu Volcano,exhibiting clear geo...The Lembang Fault is a major geological feature in West Java that borders the northern edge of Bandung(one of Indonesia’s largest cities).It lies just south of the active Tangkuban Perahu Volcano,exhibiting clear geomorphic signs of recent activity,and has been scientifically confirmed as active through geological and geophysical studies.In this work,we describe an Integrated along the Lembang Fault,which can be used for geodynamic research in Indonesia.We discuss the design of a seismic and Global Navigation Satellite System(GNSS)array sensor network for continuous monitoring,and report the status of monitoring stations that periodically collect highly accurate,continuous seismographic and GNSS readings,transmitting these data to a central server in Bandung for post-processing.Solutions from the array data are used to provide precise measurements of the deformation of the Earth’s surface over large distances,allowing for spatio-temporal tracking of tectonic movement,and resulting in a better understanding of seismic events in the region.In this study,our investigation revealed a significant compression rate of an estimated 13 microstrain/yr along the Lembang Fault,whereas the strain rate is much smaller farther south of the fault.This study presents the design of a seismo-geodetic observatory network that can be implemented in earthquake-prone regions for mitigation purposes,with particular utility for studying other active faults that also traverse populated areas in Indonesia.展开更多
The Tibetan plateau as one of the youngest orogen on the Earth was considered as the result of continent-continent collision between the Eurasian and Indian plates. The thickness and structure of the crust beneath Tib...The Tibetan plateau as one of the youngest orogen on the Earth was considered as the result of continent-continent collision between the Eurasian and Indian plates. The thickness and structure of the crust beneath Tibetan plateau is essential to understand deformation behavior of the plateau. Active-source seismic profiling is most available geophysical method for imaging the structure of the continental crust. The results from more than 25 active-sources seismic profiles carried out in the past twenty years were reviewed in this article. A preliminary cross crustal pattern of the Tibetan Plateau was presented and discussed. The Moho discontinuity buries at the range of 60-80 km on average and have steep ramps located roughly beneath the sutures that are compatible with the successive stacking/accretion of the former Cenozoic blocks northeastward. The deepest Moho （near 80 km） appears closely near IYS and the crustal scale thrust system beneath southern margin of Tibetan plateau suggests strong dependence on collision and non-distributed deformation there. However, the -20 km order of Moho offsets hardly reappears in the inline section across northern Tibetan plateau. Without a universally accepted, convincing dynamic explanation model accommodated the all of the facts seen in controlled seismic sections, but vertical thickening and northeastern shorten of the crust is quite evident and interpretable to a certain extent as the result of continent-continent collision. Simultaneously, weak geophysical signature of the BNS suggests that convergence has been accommodated perhaps partially through pure-shear thickening accompanied by removal of lower crustal material by lateral escape. Recent years the result of Moho with -7 km offset and long extend in south-dip angle beneath the east Kunlun orogen and a grand thrust fault at the northern margin of Qilian orogen has attract more attention to action from the northern blocks. The broad lower-velocity area in the upper-middle crust of the Lhasa block was once considered as resulted from partially melted rocks. However the low normal vp/vs ratio and the Moho stepwise rise fail to support significant partial melting in the middle-lower crust of the central-northern Tibetan plateau. Furthermore, the lower-velocity of crust occasionally disappears, and/or local thinned exhibits their non-stationary spatial distribution.展开更多
Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non- regular geom...Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non- regular geometries of the fracture systems. However, no adequate efforts have been made to study this issue due to the current practical impossibility of laboratory tests with samples of large volumes con- taining many fractures, and the difficulty for controlling reliable initial and boundary conditions for large-scale in situ tests. Therefore, a reliable numerical predicting approach for evaluating anisotropy of fractured rock masses is needed. The objective of this study is to systematically investigate anisotropy of strength and deformability of fractured rocks, which has not been conducted in the past, using a nu- merical modeling method. A series of realistic two-dimensional （2D） discrete fracture network （DFN） models were established based on site investigation data, which were then loaded in different directions, using the code UDEC of discrete element method （DEM）, with changing confining pressures. Numerical results show that strength envelopes and elastic deformability parameters of tested numerical models are significantly anisotropic, and vary with changing axial loading and confining pressures. The results indicate that for design and safety assessments of rock engineering projects, the directional variations of strength and deformability of the fractured rock mass concerned must be treated properly with respect to the directions of in situ stresses. Traditional practice for simply positioning axial orientation of tunnels in association with principal stress directions only may not be adequate for safety requirements. Outstanding issues of the present study and su^zestions for future study are also oresented.展开更多
Knowledge of the strength and deformability of fractured rocks is important for design, construction and stability evaluation of slopes, foundations and underground excavations in civil and mining engineering. However...Knowledge of the strength and deformability of fractured rocks is important for design, construction and stability evaluation of slopes, foundations and underground excavations in civil and mining engineering. However, laboratory tests of intact rock samples cannot provide information about the strength and deformation behaviors of fractured rock masses that include many fractures of varying sizes, orientations and locations. On the other hand, large-scale in situ tests of fractured rock masses are economically costly and often not practical in reality at present. Therefore, numerical modeling becomes necessary. Numerical predicting using discrete element methods(DEM) is a suitable approach for such modeling because of their advantages of explicit representations of both fractures system geometry and their constitutive behaviors of fractures, besides that of intact rock matrix. In this study, to generically determine the compressive strength of fractured rock masses, a series of numerical experiments were performed on two-dimensional discrete fracture network models based on the realistic geometrical and mechanical data of fracture systems from feld mapping. We used the UDEC code and a numerical servo-controlled program for controlling the progressive compressive loading process to avoid sudden violent failure of the models. The two loading conditions applied are similar to the standard laboratory testing for intact rock samples in order to check possible differences caused by such loading conditions. Numerical results show that the strength of fractured rocks increases with the increasing confning pressure, and that deformation behavior of fractured rocks follows elasto-plastic model with a trend of strain hardening. The stresses and strains obtained from these numerical experiments were used to ft the well-known Mohr-Coulomb(MC) and Hoek-Brown(H-B) failure criteria, represented by equivalent material properties defning these two criteria. The results show that both criteria can provide fair estimates of the compressive strengths for all tested numerical models. Parameters of the elastic deformability of fractured models during elastic deformation stages were also evaluated, and represented as equivalent Young’s modulus and Poisson’s ratio as functions of lateral confning pressure. It is the frst time that such systematic numerical predicting for strength of fractured rocks was performed considering different loading conditions, with important fndings for different behaviors of fractured rock masses, compared with testing intact rock samples under similar loading conditions.展开更多
This study investigates the relation between the Coulomb failure stress of the mainshock with the aftershocks sequence following the 2018 Palu-Donggala earthquake in Indonesia.We calculate the Coulomb failure stress u...This study investigates the relation between the Coulomb failure stress of the mainshock with the aftershocks sequence following the 2018 Palu-Donggala earthquake in Indonesia.We calculate the Coulomb failure stress using the available coseismic fault models,which had varied moment magnitudes between M_W7.53~M_W7.62.Different interpretations of the fault sources were suggested by previous studies.While two fault models suggested that one inland fault segment ruptured during the earthquake,another fault model proposed that two fault segments ruptured inland of Central Sulawesi and along the coast of Palu bay.We further overlay the positive and negative values of Coulomb failure stress with the reported relocated aftershock.We find that only by conducting Coulomb failure stress analysis,we can not favour the preference of the coseismic fault which explains aftershock distribution.This investigation demonstrates that additional observational data from geological field surveys are required to identify the surface rupture in comparison with the coseismic fault model.展开更多
Research on strain anomalies and large earthquakes based on temporal and spatial crustal activities has been rapidly growing due to data availability, especially in Japan and Indonesia. However, many research works us...Research on strain anomalies and large earthquakes based on temporal and spatial crustal activities has been rapidly growing due to data availability, especially in Japan and Indonesia. However, many research works used local-scale case studies that focused on a specific earthquake characteristic using knowledgedriven techniques, such as crustal deformation analysis. In this study, a data-driven-based analysis is used to detect anomalies using displacement rates and deformation pattern features extracted from daily global navigation satellite system(GNSS) data using a machine learning algorithm. The GNSS data with188 and 1181 continuously operating reference stations from Indonesia and Japan, respectively, are used to identify the anomaly of recent major earthquakes in the last two decades. Feature displacement rates and deformation patterns are processed in several window times with 2560 experiment scenarios to produce the best detection using tree-based algorithms. Tree-based algorithms with a single estimator(decision tree), ensemble bagging(bagging, random forest and Extra Trees), and ensemble boosting(AdaBoost, gradient boosting, LGBM, and XGB) are applied in the study. The experiment test using realtime scenario GNSSdailydatareveals high F1-scores and accuracy for anomaly detection using slope windowing 365 and 730 days of 91-day displacement rates and then 7-day deformation pattern features in tree-based algorithms. The results show the potential for medium-term anomaly detection using GNSS data without the need for multiple vulnerability assessments.展开更多
An important characteristic of fractured rocks is their high seismic attenuation, which so far has been mainly attributed to wave-induced fluid flow（WIFF） between the fractures and the embedding matrix. The influenc...An important characteristic of fractured rocks is their high seismic attenuation, which so far has been mainly attributed to wave-induced fluid flow（WIFF） between the fractures and the embedding matrix. The influence of fracture connectivity on seismic attenuation has, however, recently, only been investigated. Numerical compressibility and shear tests based on Biot＇s quasi-static poro-elastic equations illustrate that an important manifestation of WIFF arises in the presence of fracture connectivity. The corresponding energy loss, which can be significant for both P- and S-waves, is mainly due to fluid flow within the connected fractures and is sensitive to the permeabilities as well as the lengths and intersection angles of the fractures. Correspondingly, this phenomenon contains valuable information on the governing hydraulic properties of fractured rocks and hence should be accounted for whenever realistic seismic models of such media are needed.展开更多
We carried out time-lapse analysis in a producing Niger Delta X-field, by first investigating the response and sensitivity of rock properties/attributes to lithology and pore fill in 3-D cross plot domain and by Gassm...We carried out time-lapse analysis in a producing Niger Delta X-field, by first investigating the response and sensitivity of rock properties/attributes to lithology and pore fill in 3-D cross plot domain and by Gassmann’s fluid substitution modeling. Furthermore, 4-D seismic data were inverted into acoustic impedance volumes through model based inversion scheme. This served as input into a multi-attribute neural network algorithm for the extraction of rock attribute volumes based on the results of the petrophysical log analysis. Subsequently, horizon slices of rock properties/ attributes were extracted from the inverted seismic data and analyzed. In this way, we mapped hydrocarbon depleted wells in the field, and identified probable by-passed hydrocarbon zones. Thus, the integration of well and time lapse seismic (4-D) data in reservoir studies has remarkably improved information on the reservoir economic potential, and enhanced hydrocarbon recovery factor.展开更多
The relationship between geology and landforms has long been established with quantitative analysis dating back more than 100 years. The surface expression of various subsurface lithologies motivates our effort to dev...The relationship between geology and landforms has long been established with quantitative analysis dating back more than 100 years. The surface expression of various subsurface lithologies motivates our effort to develop an automated terrain classification algorithm based solely on topographic information. The nexus of several factors has recently provided the opportunity to advance our understanding of the relationship between topography and geology within a rigorous quantitative framework, including recent advances in the field of geomorphometrics (the science of quantitative land surface analysis), the availability of very high resolution (sub meter) digital elevation models, and increasing sophisticated geomorphology and image analysis techniques. In the present study, the geological and geomorphological units in an exemplar study area located in Western U.S. (southern Nevada) have been delineated through an evaluation of a high resolution (1-meter and 0.25-meter) digital elevation model. The morphological aspects of these features obtained from DEMs generated from different sources are compared. Our analysis demonstrates that a 1-meter DEM can provide a terrain characterization that can differentiate underlying lithological types and a very high resolution DEM (0.25 meter) can be used to evaluate fracture patterns.展开更多
The well-known non-uniqueness in modeling of potential-field data results in an infinite number of models that fit the data almost equally. This non-uniqueness concept is exploited to devise a method to transform the ...The well-known non-uniqueness in modeling of potential-field data results in an infinite number of models that fit the data almost equally. This non-uniqueness concept is exploited to devise a method to transform the magnetic data based on their equivalent-source. The unconstrained 3D magnetic inversion modeling is used to obtain the anomalous sources, i.e. 3D magnetization distribution in the subsurface. Although the 3D model fitting the data is not geologically feasible, it can serve as an equivalent-source. The transformations, which are commonly applied to magnetic data (reduction to the pole, reduction to the equator, upward and downward continuation), are the response of the equivalent-source with appropriate kernel functions. The application of the method to both synthetic and field data showed that the transformation of magnetic data using the 3D equivalent-source gave satisfactory results. The method is relatively more stable than the filtering technique, with respect to the noise present in the data.展开更多
The difficulty in achieving well-to-seismic ties due to errors arising from wrong time-to-depth conversions has been as a result of ignoring anisotropy in seismic processing. Anisotropy plays a vital role in the proce...The difficulty in achieving well-to-seismic ties due to errors arising from wrong time-to-depth conversions has been as a result of ignoring anisotropy in seismic processing. Anisotropy plays a vital role in the processing and interpretation of seismic data. In this work, an inversion method based on the elastic stiffness tensors was adopted to estimate and quantify anisotropy in two depobelts using petrophysical well logs in Niger delta (Central Swamp and Greater Ughelli). Results show that the estimated delta (δ), epsilon (ε), gamma (γ) and eta (η) exhibit a high degree of anisotropy in the shales than in the sands. The parameters were observed to be higher in the Central Swamp than the Greater Ughelli depobelt. This behavior could be associated with the alternating sequence of massive shale and sand beds geologically observed within this depobelt. This work was also able to derive empirical relations that could be used in estimating these parameters in the depobelts once appropriate information or data for any one parameter is available.展开更多
Hydraulic and layer parameters of groundwater aquifer have been evaluated in parts of Buruku and Gboko local government area councils, for the primary purpose of assessing quality and potential of groundwater in the a...Hydraulic and layer parameters of groundwater aquifer have been evaluated in parts of Buruku and Gboko local government area councils, for the primary purpose of assessing quality and potential of groundwater in the areas. A total of 18 Vertical Electrical Sounding (VES) stations were occupied along traverse lines using the Schlumberger electrode configuration. The results revealed a characteristic QQA, QHH and QH type curves, with 6 - 7 geoelectric subsurface layers. The geoelectric layers are dominantly sandy with intercalations of shale at shallow depths in most stations. The aquiferous layers were delineated at the fourth and fifth geoelectric layers with average aquifer resistivity and depth of 420.56 Ω·m and 69.1 m, respectively. Groundwater flow is generally from the northeast to the southwest in line with the tectonics of the Benue trough. Two potential groundwater zones were delineated. These are the zone of poor quality water to the north (central) and east of the area of high potential and the zone of quality groundwater to the northeast, west and southwest of low potential. The study revealed that productive boreholes for excellent and sustainable yields were more viable in the northern (central) and eastern parts of the study area than in the northeast, west and southwest parts.展开更多
The internal energy of the Solid Earth is mainly transferred through thermal convection of the mantle.Here,we discuss the 10^(20)-J-scale energy relating to the dynamics of the Solid Earth’s interior.The energy relea...The internal energy of the Solid Earth is mainly transferred through thermal convection of the mantle.Here,we discuss the 10^(20)-J-scale energy relating to the dynamics of the Solid Earth’s interior.The energy released from the interior of the present-day Earth to outer space per year is estimated as E_(earth)=1.4×10^(21) J yr^(-1) based on the recent dataset of globally observed crustal heat flow,which is a factor of two or three times larger than the annual energy consumption of the total population of the world,5.7×10^(20) J yr^(-1).Of the energy from global crustal heat flow,the energy released by all of the major hotspot plumes in volcanic vents per year is estimated as E_(plume)=7.2×10^(19) J yr^(-1),which is approximately only 6%of the Eearth.We propose that a large number of mantle plumes have not emerged as hotspots on the Earth’s surface,with the possibility that Eplume is larger than expected if the energy released from small seamounts of the Earth is considered.Considering the heat(energy)budget of the Earth,the heat production by the decay of radioactive isotopes in the mantle and crust is nearly comparable to the heat released by the secular cooling of the Earth.Of Eearth,the annual energy released by the secular cooling of the Earth is estimated as 6.6×10_(20) J yr^(-1).This energy is closely related to the geothermal energy from our planet.展开更多
Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features aro...Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features around Merapi are very attractive to be investigated because they have been formed by a complex tectonic process and volcanic activities since tens of millions of years ago. The southern mountain range, Kendeng basin and Opak active fault located around the study area resulted from these processes. DOMERAPI project was conducted to understand deep magma sources of the Merapi volcano comprehensively. The DOMERAPI network was running from October 2013 to mid-April 2015 by deploying 46 broad-band seismometers around the volcano. Several steps, i.e., earthquake event identification,arrival time picking of P and S waves, hypocenter determination and hypocenter relocation, were carried out in this study. We used Geiger＇s method（Geiger 1912） for hypocenter determination and double-difference method for hypocenter relocation. The relocation result will be used to carry out seismic tomographic imaging of structures beneath the Merapi volcano and its surroundings. For the hypocenter determination, the DOMERAPI data were processed simultaneously with those from the Agency for Meteorology, Climatology and Geophysics（BMKG） seismic network in order to minimize the azimuthal gap. We found that the majority of earthquakes occurred outside the DOMERAPI network. There are 464 and 399 earthquakes obtained before and after hypocenter relocation, respectively. The hypocenter relocation result successfully detects some tectonic features, such as a nearly vertical cluster of events indicating a subduction-related backthrust to the south of central Java and a cluster of events to the east of Opak fault suggesting that the fault has an eastward dip.展开更多
Sokor Formation reservoir intervals are intrinsically anisotropic,heterogeneous and with a characteristic of Low Contrast Low Resistivity(LCLR)log responses in parts of the Termit basin.Discriminating sands from shale...Sokor Formation reservoir intervals are intrinsically anisotropic,heterogeneous and with a characteristic of Low Contrast Low Resistivity(LCLR)log responses in parts of the Termit basin.Discriminating sands from shales/mudstones and hydrocarbon sands from brine sands as well as accurately evaluating the distribution of relevant reservoir properties using conventional seismic interpretation are complicated,and undermines reservoir characterization in such reservoirs.To enhance reservoir evaluation and reduce development planning and production risks,rock physics analysis was intergrated into the petrophysical workflow,which fed higher fidelity inputs into a post stack seismic inversion workflow.Rock Physics Diagnostics(RPD)analysis revealed that the reservoir interval of interest has grain size distribution of different lithologies,which is related to the environment of deposition and burial history,and could be best described by the constant cement sand model.The rock physics analyses revealed that facies were most effectively discriminated based on their Vp/Vs ratios and acoustic impedance.Particularly,hydrocarbon saturated sandstones,brine saturated shaly sandstones and shales/mudstones which exhibit similar acoustic impedance characteristics,were clearly discriminated by their Vp/Vs.The inverted seismic attributes as well as Seismic Based-Rock Physics Templates(RPT),clearly delineated the hydrocarbon fields,predicted new prospects beyond the existing well locations,which could be considered for field appraisal or development opportunities in the basin.These results demonstrate the value of the robust application of rock physics diagnostic modeling and seismic inversion in quantitative reservoir characterization and may be quite useful in undrilled locations in the basins and fields with similar geology.展开更多
Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface models.Conventional full-waveform inversion requires an accu-rate estimation of the source wavelet,and its computational c...Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface models.Conventional full-waveform inversion requires an accu-rate estimation of the source wavelet,and its computational cost is high.We develop a novel source-independent full-waveform inversion method using a hybrid time-and frequency-domain scheme to avoid the requirement of source wavelet estimation and to reduce the computational cost.We employ an amplitude-semblance objective function to not only effectively remove the source wavelet effect on full-waveform inver-sion,but also to eliminate the impact of the inconsistency of source wavelets among different shot gathers on full-waveform inversion.To reduce the high computational cost of full-waveform inversion in the time domain,we implement our new algorithm using a hybrid time-and frequency-domain approach.The forward and backward wave propagation operations are conducted in the time domain,while the frequency-domain wavefields are obtained during modeling using the discrete-time Fourier trans-form.The inversion process is conducted in the frequency domain for selected frequen-cies.We verify our method using synthetic seismic data for the Marmousi model.The results demonstrate that our novel source-independent full-waveform inversion pro-duces accurate velocity models even if the source signature is incorrect.In addition,our method can significantly reduce the computational time using the hybrid time-and frequency-domain approach compared to the conventional full-waveform inversion in the time domain.展开更多
Reliable subsurface time-lapse seismic monitoring is crucial for many geo-physical applications,such as enhanced geothermal system characterization,geologic carbon utilization and storage,and conventional and unconven...Reliable subsurface time-lapse seismic monitoring is crucial for many geo-physical applications,such as enhanced geothermal system characterization,geologic carbon utilization and storage,and conventional and unconventional oil/gas reservoir characterization,etc.We develop an elastic-wave sensitivity propagation method for optimal design of cost-effective time-lapse seismic surveys considering the fact that most of subsurface geologic layers and fractured reservoirs are anisotropic instead of isotropic.For anisotropic media,we define monitoring criteria using qP-and qS-wave sensitivity energies after decomposing qP-and qS-wave components from the total elastic-wave sensitivity wavefield using a hybrid time-and frequency-domain approach.Geophones should therefore be placed at locations with significant qP-and qS-wave sensitivity energies for cost-effective time-lapse seismic monitoring in an anisotropic geology setting.Our numerical modeling results for a modified anisotropic Hess model demonstrate that,compared with the isotropic case,subsurface anisotropy changes the spatial distributions of elastic-wave sensitivity energies.Consequently,it is necessary to consider subsurface anisotropies when designing the spatial distri-bution of geophones for cost-effective time-lapse seismic monitoring.This finding suggests that it is essential to use our new anisotropic elastic-wave sensitivity modeling method for optimal design of time-lapse seismic surveys to reliably monitor the changes in subsurface reservoirs,fracture zones or target monitoring regions.展开更多
基金supported by Universitas Gadjah Mada through the 2022 Indonesian Collaborative Research Program.
文摘The Mentawai Forearc Sliver(MFS)is characterized by oblique deformation formed as slip partitioned between normal and parallel trench plate convergence.The surge of great earthquakes from 2004 to2012 along the adjacent Sunda trench left a large unbroken segment known as the Mentawai Seismic Gap.Here,we adopted continuous Global Navigation Satellite System(GNSS)observation data to identify the present regional crustal deformation using geodetic strain rates.The principal strain rate,dilatation rate,and maximum shear strain rate are about 0.13 microstrain/yr,0.2 microstrain/yr,and 0.1 microstrain/yr,respectively,with the range of its uncertainties between 0.01 and 0.04 microstrain/yr.The dilatation and maximum shear strain rates reveal the spatial coverage of strike-slip duplex and backthrust tectonics along the Mentawai Forearc Sliver.
基金the National Research and InnovationAgency of Indonesia (BRIN) under research grant Rumah Program Kebencanaan 2022-2025support from the Earth Observatory Singapore (EOS)supported by the Ministry of Higher Education, Science,and Technology, and Institut Teknologi Bandung through the Indonesian Collaborative Research Program.
文摘The Lembang Fault is a major geological feature in West Java that borders the northern edge of Bandung(one of Indonesia’s largest cities).It lies just south of the active Tangkuban Perahu Volcano,exhibiting clear geomorphic signs of recent activity,and has been scientifically confirmed as active through geological and geophysical studies.In this work,we describe an Integrated along the Lembang Fault,which can be used for geodynamic research in Indonesia.We discuss the design of a seismic and Global Navigation Satellite System(GNSS)array sensor network for continuous monitoring,and report the status of monitoring stations that periodically collect highly accurate,continuous seismographic and GNSS readings,transmitting these data to a central server in Bandung for post-processing.Solutions from the array data are used to provide precise measurements of the deformation of the Earth’s surface over large distances,allowing for spatio-temporal tracking of tectonic movement,and resulting in a better understanding of seismic events in the region.In this study,our investigation revealed a significant compression rate of an estimated 13 microstrain/yr along the Lembang Fault,whereas the strain rate is much smaller farther south of the fault.This study presents the design of a seismo-geodetic observatory network that can be implemented in earthquake-prone regions for mitigation purposes,with particular utility for studying other active faults that also traverse populated areas in Indonesia.
基金financed by the Ministry of Land and Resources of China (2004DKA20280-2-5)International Sciences and Technology cooperation (2006DFA21340)+5 种基金the special funds for Sciences and technology research of public welfare trades (200811021)the key innovation project for sciences and technology of Ministry of Land and Resources (1212010711813)the China Geology survey Bureau and resources land investigation project(1212010611809)the Basic outlay of scientific research work from Ministry of Science and Technology of the People's Republic of China (J0803)the National Natural Science Foundation of China (40830316 and 40874045)SINOPPROBE-Ⅱ and Open Fund (NO.GDL0603_) of Key Laboratory of Geo-detection (China University of Geosciences,Beijing),Ministry of Education"
文摘The Tibetan plateau as one of the youngest orogen on the Earth was considered as the result of continent-continent collision between the Eurasian and Indian plates. The thickness and structure of the crust beneath Tibetan plateau is essential to understand deformation behavior of the plateau. Active-source seismic profiling is most available geophysical method for imaging the structure of the continental crust. The results from more than 25 active-sources seismic profiles carried out in the past twenty years were reviewed in this article. A preliminary cross crustal pattern of the Tibetan Plateau was presented and discussed. The Moho discontinuity buries at the range of 60-80 km on average and have steep ramps located roughly beneath the sutures that are compatible with the successive stacking/accretion of the former Cenozoic blocks northeastward. The deepest Moho （near 80 km） appears closely near IYS and the crustal scale thrust system beneath southern margin of Tibetan plateau suggests strong dependence on collision and non-distributed deformation there. However, the -20 km order of Moho offsets hardly reappears in the inline section across northern Tibetan plateau. Without a universally accepted, convincing dynamic explanation model accommodated the all of the facts seen in controlled seismic sections, but vertical thickening and northeastern shorten of the crust is quite evident and interpretable to a certain extent as the result of continent-continent collision. Simultaneously, weak geophysical signature of the BNS suggests that convergence has been accommodated perhaps partially through pure-shear thickening accompanied by removal of lower crustal material by lateral escape. Recent years the result of Moho with -7 km offset and long extend in south-dip angle beneath the east Kunlun orogen and a grand thrust fault at the northern margin of Qilian orogen has attract more attention to action from the northern blocks. The broad lower-velocity area in the upper-middle crust of the Lhasa block was once considered as resulted from partially melted rocks. However the low normal vp/vs ratio and the Moho stepwise rise fail to support significant partial melting in the middle-lower crust of the central-northern Tibetan plateau. Furthermore, the lower-velocity of crust occasionally disappears, and/or local thinned exhibits their non-stationary spatial distribution.
文摘Anisotropy of the strength and deformation behaviors of fractured rock masses is a crucial issue for design and stability assessments of rock engineering structures, due mainly to the non-uniform and non- regular geometries of the fracture systems. However, no adequate efforts have been made to study this issue due to the current practical impossibility of laboratory tests with samples of large volumes con- taining many fractures, and the difficulty for controlling reliable initial and boundary conditions for large-scale in situ tests. Therefore, a reliable numerical predicting approach for evaluating anisotropy of fractured rock masses is needed. The objective of this study is to systematically investigate anisotropy of strength and deformability of fractured rocks, which has not been conducted in the past, using a nu- merical modeling method. A series of realistic two-dimensional （2D） discrete fracture network （DFN） models were established based on site investigation data, which were then loaded in different directions, using the code UDEC of discrete element method （DEM）, with changing confining pressures. Numerical results show that strength envelopes and elastic deformability parameters of tested numerical models are significantly anisotropic, and vary with changing axial loading and confining pressures. The results indicate that for design and safety assessments of rock engineering projects, the directional variations of strength and deformability of the fractured rock mass concerned must be treated properly with respect to the directions of in situ stresses. Traditional practice for simply positioning axial orientation of tunnels in association with principal stress directions only may not be adequate for safety requirements. Outstanding issues of the present study and su^zestions for future study are also oresented.
文摘Knowledge of the strength and deformability of fractured rocks is important for design, construction and stability evaluation of slopes, foundations and underground excavations in civil and mining engineering. However, laboratory tests of intact rock samples cannot provide information about the strength and deformation behaviors of fractured rock masses that include many fractures of varying sizes, orientations and locations. On the other hand, large-scale in situ tests of fractured rock masses are economically costly and often not practical in reality at present. Therefore, numerical modeling becomes necessary. Numerical predicting using discrete element methods(DEM) is a suitable approach for such modeling because of their advantages of explicit representations of both fractures system geometry and their constitutive behaviors of fractures, besides that of intact rock matrix. In this study, to generically determine the compressive strength of fractured rock masses, a series of numerical experiments were performed on two-dimensional discrete fracture network models based on the realistic geometrical and mechanical data of fracture systems from feld mapping. We used the UDEC code and a numerical servo-controlled program for controlling the progressive compressive loading process to avoid sudden violent failure of the models. The two loading conditions applied are similar to the standard laboratory testing for intact rock samples in order to check possible differences caused by such loading conditions. Numerical results show that the strength of fractured rocks increases with the increasing confning pressure, and that deformation behavior of fractured rocks follows elasto-plastic model with a trend of strain hardening. The stresses and strains obtained from these numerical experiments were used to ft the well-known Mohr-Coulomb(MC) and Hoek-Brown(H-B) failure criteria, represented by equivalent material properties defning these two criteria. The results show that both criteria can provide fair estimates of the compressive strengths for all tested numerical models. Parameters of the elastic deformability of fractured models during elastic deformation stages were also evaluated, and represented as equivalent Young’s modulus and Poisson’s ratio as functions of lateral confning pressure. It is the frst time that such systematic numerical predicting for strength of fractured rocks was performed considering different loading conditions, with important fndings for different behaviors of fractured rock masses, compared with testing intact rock samples under similar loading conditions.
基金supported by the 2019 World Class University Research Fund of Bandung Institute of Technology for International Research No.LPPM.PN-10-30-2019the 2018 Overseas Research Grants of the Asahi Glass Foundation No.FTTM.PN-5-01-2019
文摘This study investigates the relation between the Coulomb failure stress of the mainshock with the aftershocks sequence following the 2018 Palu-Donggala earthquake in Indonesia.We calculate the Coulomb failure stress using the available coseismic fault models,which had varied moment magnitudes between M_W7.53~M_W7.62.Different interpretations of the fault sources were suggested by previous studies.While two fault models suggested that one inland fault segment ruptured during the earthquake,another fault model proposed that two fault segments ruptured inland of Central Sulawesi and along the coast of Palu bay.We further overlay the positive and negative values of Coulomb failure stress with the reported relocated aftershock.We find that only by conducting Coulomb failure stress analysis,we can not favour the preference of the coseismic fault which explains aftershock distribution.This investigation demonstrates that additional observational data from geological field surveys are required to identify the surface rupture in comparison with the coseismic fault model.
基金the Program PenelitianKolaborasi Indonesia(PPKI)Non APBN Universitas Diponegoro Universitas Diponegoro Indonesia under Grant 117-03/UN7.6.1/PP/2021.
文摘Research on strain anomalies and large earthquakes based on temporal and spatial crustal activities has been rapidly growing due to data availability, especially in Japan and Indonesia. However, many research works used local-scale case studies that focused on a specific earthquake characteristic using knowledgedriven techniques, such as crustal deformation analysis. In this study, a data-driven-based analysis is used to detect anomalies using displacement rates and deformation pattern features extracted from daily global navigation satellite system(GNSS) data using a machine learning algorithm. The GNSS data with188 and 1181 continuously operating reference stations from Indonesia and Japan, respectively, are used to identify the anomaly of recent major earthquakes in the last two decades. Feature displacement rates and deformation patterns are processed in several window times with 2560 experiment scenarios to produce the best detection using tree-based algorithms. Tree-based algorithms with a single estimator(decision tree), ensemble bagging(bagging, random forest and Extra Trees), and ensemble boosting(AdaBoost, gradient boosting, LGBM, and XGB) are applied in the study. The experiment test using realtime scenario GNSSdailydatareveals high F1-scores and accuracy for anomaly detection using slope windowing 365 and 730 days of 91-day displacement rates and then 7-day deformation pattern features in tree-based algorithms. The results show the potential for medium-term anomaly detection using GNSS data without the need for multiple vulnerability assessments.
基金supported in part by grants from the Swiss National Science Foundationthe Agencia Nacional de Promocion Cientifica y Tecnologica (No. PICT 2010-2129), Argentinathe Fondation Herbette of the University of Lausanne
文摘An important characteristic of fractured rocks is their high seismic attenuation, which so far has been mainly attributed to wave-induced fluid flow（WIFF） between the fractures and the embedding matrix. The influence of fracture connectivity on seismic attenuation has, however, recently, only been investigated. Numerical compressibility and shear tests based on Biot＇s quasi-static poro-elastic equations illustrate that an important manifestation of WIFF arises in the presence of fracture connectivity. The corresponding energy loss, which can be significant for both P- and S-waves, is mainly due to fluid flow within the connected fractures and is sensitive to the permeabilities as well as the lengths and intersection angles of the fractures. Correspondingly, this phenomenon contains valuable information on the governing hydraulic properties of fractured rocks and hence should be accounted for whenever realistic seismic models of such media are needed.
文摘We carried out time-lapse analysis in a producing Niger Delta X-field, by first investigating the response and sensitivity of rock properties/attributes to lithology and pore fill in 3-D cross plot domain and by Gassmann’s fluid substitution modeling. Furthermore, 4-D seismic data were inverted into acoustic impedance volumes through model based inversion scheme. This served as input into a multi-attribute neural network algorithm for the extraction of rock attribute volumes based on the results of the petrophysical log analysis. Subsequently, horizon slices of rock properties/ attributes were extracted from the inverted seismic data and analyzed. In this way, we mapped hydrocarbon depleted wells in the field, and identified probable by-passed hydrocarbon zones. Thus, the integration of well and time lapse seismic (4-D) data in reservoir studies has remarkably improved information on the reservoir economic potential, and enhanced hydrocarbon recovery factor.
文摘The relationship between geology and landforms has long been established with quantitative analysis dating back more than 100 years. The surface expression of various subsurface lithologies motivates our effort to develop an automated terrain classification algorithm based solely on topographic information. The nexus of several factors has recently provided the opportunity to advance our understanding of the relationship between topography and geology within a rigorous quantitative framework, including recent advances in the field of geomorphometrics (the science of quantitative land surface analysis), the availability of very high resolution (sub meter) digital elevation models, and increasing sophisticated geomorphology and image analysis techniques. In the present study, the geological and geomorphological units in an exemplar study area located in Western U.S. (southern Nevada) have been delineated through an evaluation of a high resolution (1-meter and 0.25-meter) digital elevation model. The morphological aspects of these features obtained from DEMs generated from different sources are compared. Our analysis demonstrates that a 1-meter DEM can provide a terrain characterization that can differentiate underlying lithological types and a very high resolution DEM (0.25 meter) can be used to evaluate fracture patterns.
文摘The well-known non-uniqueness in modeling of potential-field data results in an infinite number of models that fit the data almost equally. This non-uniqueness concept is exploited to devise a method to transform the magnetic data based on their equivalent-source. The unconstrained 3D magnetic inversion modeling is used to obtain the anomalous sources, i.e. 3D magnetization distribution in the subsurface. Although the 3D model fitting the data is not geologically feasible, it can serve as an equivalent-source. The transformations, which are commonly applied to magnetic data (reduction to the pole, reduction to the equator, upward and downward continuation), are the response of the equivalent-source with appropriate kernel functions. The application of the method to both synthetic and field data showed that the transformation of magnetic data using the 3D equivalent-source gave satisfactory results. The method is relatively more stable than the filtering technique, with respect to the noise present in the data.
文摘The difficulty in achieving well-to-seismic ties due to errors arising from wrong time-to-depth conversions has been as a result of ignoring anisotropy in seismic processing. Anisotropy plays a vital role in the processing and interpretation of seismic data. In this work, an inversion method based on the elastic stiffness tensors was adopted to estimate and quantify anisotropy in two depobelts using petrophysical well logs in Niger delta (Central Swamp and Greater Ughelli). Results show that the estimated delta (δ), epsilon (ε), gamma (γ) and eta (η) exhibit a high degree of anisotropy in the shales than in the sands. The parameters were observed to be higher in the Central Swamp than the Greater Ughelli depobelt. This behavior could be associated with the alternating sequence of massive shale and sand beds geologically observed within this depobelt. This work was also able to derive empirical relations that could be used in estimating these parameters in the depobelts once appropriate information or data for any one parameter is available.
文摘Hydraulic and layer parameters of groundwater aquifer have been evaluated in parts of Buruku and Gboko local government area councils, for the primary purpose of assessing quality and potential of groundwater in the areas. A total of 18 Vertical Electrical Sounding (VES) stations were occupied along traverse lines using the Schlumberger electrode configuration. The results revealed a characteristic QQA, QHH and QH type curves, with 6 - 7 geoelectric subsurface layers. The geoelectric layers are dominantly sandy with intercalations of shale at shallow depths in most stations. The aquiferous layers were delineated at the fourth and fifth geoelectric layers with average aquifer resistivity and depth of 420.56 Ω·m and 69.1 m, respectively. Groundwater flow is generally from the northeast to the southwest in line with the tectonics of the Benue trough. Two potential groundwater zones were delineated. These are the zone of poor quality water to the north (central) and east of the area of high potential and the zone of quality groundwater to the northeast, west and southwest of low potential. The study revealed that productive boreholes for excellent and sustainable yields were more viable in the northern (central) and eastern parts of the study area than in the northeast, west and southwest parts.
文摘The internal energy of the Solid Earth is mainly transferred through thermal convection of the mantle.Here,we discuss the 10^(20)-J-scale energy relating to the dynamics of the Solid Earth’s interior.The energy released from the interior of the present-day Earth to outer space per year is estimated as E_(earth)=1.4×10^(21) J yr^(-1) based on the recent dataset of globally observed crustal heat flow,which is a factor of two or three times larger than the annual energy consumption of the total population of the world,5.7×10^(20) J yr^(-1).Of the energy from global crustal heat flow,the energy released by all of the major hotspot plumes in volcanic vents per year is estimated as E_(plume)=7.2×10^(19) J yr^(-1),which is approximately only 6%of the Eearth.We propose that a large number of mantle plumes have not emerged as hotspots on the Earth’s surface,with the possibility that Eplume is larger than expected if the energy released from small seamounts of the Earth is considered.Considering the heat(energy)budget of the Earth,the heat production by the decay of radioactive isotopes in the mantle and crust is nearly comparable to the heat released by the secular cooling of the Earth.Of Eearth,the annual energy released by the secular cooling of the Earth is estimated as 6.6×10_(20) J yr^(-1).This energy is closely related to the geothermal energy from our planet.
基金Institut de Recherche pour le Développement (IRD), France, for funding the DOMERAPI projectCenter for Volcanology and Geohazard Mitigation as the main counterpart of the DOMERAPI project in Indonesia+1 种基金supported in part by the Indonesian Directorate General of Higher Education (DIKTI) research funding 2015–2016the Institut Teknologi Bandung (ITB) through a WCU research Grant 2016 awarded to SW
文摘Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features around Merapi are very attractive to be investigated because they have been formed by a complex tectonic process and volcanic activities since tens of millions of years ago. The southern mountain range, Kendeng basin and Opak active fault located around the study area resulted from these processes. DOMERAPI project was conducted to understand deep magma sources of the Merapi volcano comprehensively. The DOMERAPI network was running from October 2013 to mid-April 2015 by deploying 46 broad-band seismometers around the volcano. Several steps, i.e., earthquake event identification,arrival time picking of P and S waves, hypocenter determination and hypocenter relocation, were carried out in this study. We used Geiger＇s method（Geiger 1912） for hypocenter determination and double-difference method for hypocenter relocation. The relocation result will be used to carry out seismic tomographic imaging of structures beneath the Merapi volcano and its surroundings. For the hypocenter determination, the DOMERAPI data were processed simultaneously with those from the Agency for Meteorology, Climatology and Geophysics（BMKG） seismic network in order to minimize the azimuthal gap. We found that the majority of earthquakes occurred outside the DOMERAPI network. There are 464 and 399 earthquakes obtained before and after hypocenter relocation, respectively. The hypocenter relocation result successfully detects some tectonic features, such as a nearly vertical cluster of events indicating a subduction-related backthrust to the south of central Java and a cluster of events to the east of Opak fault suggesting that the fault has an eastward dip.
文摘Sokor Formation reservoir intervals are intrinsically anisotropic,heterogeneous and with a characteristic of Low Contrast Low Resistivity(LCLR)log responses in parts of the Termit basin.Discriminating sands from shales/mudstones and hydrocarbon sands from brine sands as well as accurately evaluating the distribution of relevant reservoir properties using conventional seismic interpretation are complicated,and undermines reservoir characterization in such reservoirs.To enhance reservoir evaluation and reduce development planning and production risks,rock physics analysis was intergrated into the petrophysical workflow,which fed higher fidelity inputs into a post stack seismic inversion workflow.Rock Physics Diagnostics(RPD)analysis revealed that the reservoir interval of interest has grain size distribution of different lithologies,which is related to the environment of deposition and burial history,and could be best described by the constant cement sand model.The rock physics analyses revealed that facies were most effectively discriminated based on their Vp/Vs ratios and acoustic impedance.Particularly,hydrocarbon saturated sandstones,brine saturated shaly sandstones and shales/mudstones which exhibit similar acoustic impedance characteristics,were clearly discriminated by their Vp/Vs.The inverted seismic attributes as well as Seismic Based-Rock Physics Templates(RPT),clearly delineated the hydrocarbon fields,predicted new prospects beyond the existing well locations,which could be considered for field appraisal or development opportunities in the basin.These results demonstrate the value of the robust application of rock physics diagnostic modeling and seismic inversion in quantitative reservoir characterization and may be quite useful in undrilled locations in the basins and fields with similar geology.
基金supported by the U.S.Department of Energy(DOE)through the Los Alamos National Laboratory(LANL),which is operated by Triad National Security,LLC,for the National Nuclear Security Administration(NNSA)of U.S.DOE under Contract No.89233218CNA000001provided by the LANL Institutional Computing Program,which is supported by the U.S.DOE NNSA under Contract No.89233218CNA000001.
文摘Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface models.Conventional full-waveform inversion requires an accu-rate estimation of the source wavelet,and its computational cost is high.We develop a novel source-independent full-waveform inversion method using a hybrid time-and frequency-domain scheme to avoid the requirement of source wavelet estimation and to reduce the computational cost.We employ an amplitude-semblance objective function to not only effectively remove the source wavelet effect on full-waveform inver-sion,but also to eliminate the impact of the inconsistency of source wavelets among different shot gathers on full-waveform inversion.To reduce the high computational cost of full-waveform inversion in the time domain,we implement our new algorithm using a hybrid time-and frequency-domain approach.The forward and backward wave propagation operations are conducted in the time domain,while the frequency-domain wavefields are obtained during modeling using the discrete-time Fourier trans-form.The inversion process is conducted in the frequency domain for selected frequen-cies.We verify our method using synthetic seismic data for the Marmousi model.The results demonstrate that our novel source-independent full-waveform inversion pro-duces accurate velocity models even if the source signature is incorrect.In addition,our method can significantly reduce the computational time using the hybrid time-and frequency-domain approach compared to the conventional full-waveform inversion in the time domain.
文摘Reliable subsurface time-lapse seismic monitoring is crucial for many geo-physical applications,such as enhanced geothermal system characterization,geologic carbon utilization and storage,and conventional and unconventional oil/gas reservoir characterization,etc.We develop an elastic-wave sensitivity propagation method for optimal design of cost-effective time-lapse seismic surveys considering the fact that most of subsurface geologic layers and fractured reservoirs are anisotropic instead of isotropic.For anisotropic media,we define monitoring criteria using qP-and qS-wave sensitivity energies after decomposing qP-and qS-wave components from the total elastic-wave sensitivity wavefield using a hybrid time-and frequency-domain approach.Geophones should therefore be placed at locations with significant qP-and qS-wave sensitivity energies for cost-effective time-lapse seismic monitoring in an anisotropic geology setting.Our numerical modeling results for a modified anisotropic Hess model demonstrate that,compared with the isotropic case,subsurface anisotropy changes the spatial distributions of elastic-wave sensitivity energies.Consequently,it is necessary to consider subsurface anisotropies when designing the spatial distri-bution of geophones for cost-effective time-lapse seismic monitoring.This finding suggests that it is essential to use our new anisotropic elastic-wave sensitivity modeling method for optimal design of time-lapse seismic surveys to reliably monitor the changes in subsurface reservoirs,fracture zones or target monitoring regions.
