Subsurface reservoirs commonly exhibit layered structures.Conventional amplitude variation with angle(AVA)inversion,which relies on the Zoeppritz equation and its approximations,often fails to accurately estimate elas...Subsurface reservoirs commonly exhibit layered structures.Conventional amplitude variation with angle(AVA)inversion,which relies on the Zoeppritz equation and its approximations,often fails to accurately estimate elastic parameters because it assumes single-interface models and ignores multiple reflections and transmission losses.To address these limitations,this study proposes a novel prestack time-frequency domain joint inversion method that utilizes the reflection matrix method(RMM)as the forward operator.The RMM accurately simulates wave propagation in layered media,while the joint inversion framework minimizes the misfit between observed and synthetic data in both the time and frequency domains.By incorporating Bayesian theory to optimize the inversion process,the method effectively balances contributions from both time-domain waveforms and frequency-domain spectral information through a weighting factor.Tests on both synthetic data and field data demonstrate that the proposed method outperforms conventional AVA inversion and time-domain waveform inversion in accuracy and robustness.Furthermore,the method demonstrates good robustness against variations in initial models,random noise,and coherent noise interference.This study provides a practical and effective approach for high-precision reservoir characterization,with potential applications in complex layered media.展开更多
The Chilean Pampean flat slab subduction segment is characterized by the nearly horizontal subduction of the Nazca Plate within the depth range of 100-120 km.Numerous seismic tomography studies have been conducted to ...The Chilean Pampean flat slab subduction segment is characterized by the nearly horizontal subduction of the Nazca Plate within the depth range of 100-120 km.Numerous seismic tomography studies have been conducted to investigate its velocity structure;however,they have used only seismic body wave data or surface wave data.As a result,the existing velocity models in the region may have relatively large uncertainties.In this study,we use body wave arrival times from earthquakes occurring in central Chile between 2014 and 2019,as well as Rayleigh wave phase velocity maps at periods of 5-80 s from ambient noise empirical Green’s functions in Chile.By jointly using body wave arrival times and surface wave dispersion data,we refine the VS model and improve earthquake locations in the central Chile subduction zone.Compared with previous velocity models,our velocity model better reveals an eastward-dipping high-velocity plate representing the subducting Nazca Plate,which is 40-50 km thick and is more consistent with the slab thickness estimated by receiver function imaging and thermal modeling.Overall,the intraslab seismicity distribution spatially correlates well with the slab high-velocity anomalies except along the subduction paths of the CopiapóRidge and Juan Fernández Ridge.Additionally,parallel low-velocity stripes are imaged beneath the subducting plate,which are likely associated with the accumulated melts.The joint inversion velocity model also resolves widespread low-velocity anomalies in the crust beneath the Central Volcanic Zone of the central Andes,likely representing crustal magma chambers for various volcanoes.展开更多
Based on the synchronous joint gravity and magnetic inversion of single interface by Pilkington and the need of revealing Cenozoic and crystalline basement thickness in the new round of oil-gas exploration, we propose...Based on the synchronous joint gravity and magnetic inversion of single interface by Pilkington and the need of revealing Cenozoic and crystalline basement thickness in the new round of oil-gas exploration, we propose a joint gravity and magnetic inversion methodfor two-layer models by concentrating on the relationship between the change of thicknessI and position of the middle layer and anomaly and discuss the effects of the key parameters. Model tests and application to field data show the validity of this method.展开更多
Multi-component exploration has many advantages over ordinary P-wave exploration. PP/PS joint AVO analysis and inversion are useful and powerful methods to discriminate between reservoir and non-productive lithology. ...Multi-component exploration has many advantages over ordinary P-wave exploration. PP/PS joint AVO analysis and inversion are useful and powerful methods to discriminate between reservoir and non-productive lithology. In this paper, we derive a new PS-wave reflection coefficient approximation equation which is more accurate at larger incidence angles. The equation is simplified for small incidence angles, which makes AVO analysis clearer and easier for angles less than 30 degrees. Based on this approximation, a PP/PS joint inversion is introduced. A real data example shows that oil sands, brine sands and shales can be differentiated based on the P- to S-wave velocity ratio from the PP/PS joint inversion. Fluid factors and Poisson＇s ratio also indicate an anomaly in the target zone at the oil well location.展开更多
Accurate determination of seismic velocity of the crust is important for understanding regional tectonics and crustal evolution of the Earth. We propose a stepwise joint linearized inversion method using surface wave ...Accurate determination of seismic velocity of the crust is important for understanding regional tectonics and crustal evolution of the Earth. We propose a stepwise joint linearized inversion method using surface wave dispersion, Rayleigh wave ZH ratio （i.e., ellipticity）, and receiver function data to better resolve 1D crustal shear wave velocity （Vs） structure. Surface wave dispersion and Rayleigh wave ZH ratio data are more sensitive to absolute variations of shear wave speed at depths, but their sensi- tivity kernels to shear wave speeds are different and complimentary. However, receiver function data are more sensitive to sharp velocity contrast （e.g., due to the existence of crustal interfaces） and Vp/Vs ratios. The stepwise inversion method takes advantages of the complementary sensitivities of each dataset to better constrain the Vs model in the crust. We firstly invert surface wave dispersion and ZH ratio data to obtain a 1D smooth absolute vs model and then incorporate receiver function data in the joint inver- sion to obtain a finer Vs model with better constraints on interface structures. Through synthetic tests, Monte Carlo error analyses, and application to real data, we demonstrate that the proposed joint inversion method can resolve robust crustal Vs structures and with little initial model dependency.展开更多
A two-dimensional forward and backward algorithm for the controlled-source audio-frequency magnetotelluric （CSAMT） method is developed to invert data in the entire region （near, transition, and far） and deal with ...A two-dimensional forward and backward algorithm for the controlled-source audio-frequency magnetotelluric （CSAMT） method is developed to invert data in the entire region （near, transition, and far） and deal with the effects of artificial sources. First, a regularization factor is introduced in the 2D magnetic inversion, and the magnetic susceptibility is updated in logarithmic form so that the inversion magnetic susceptibility is always positive. Second, the joint inversion of the CSAMT and magnetic methods is completed with the introduction of the cross gradient. By searching for the weight of the cross-gradient term in the objective function, the mutual influence between two different physical properties at different locations are avoided. Model tests show that the joint inversion based on cross-gradient theory offers better results than the single-method inversion. The 2D forward and inverse algorithm for CSAMT with source can effectively deal with artificial sources and ensures the reliability of the final joint inversion algorithm.展开更多
Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s...Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s along the fault strike direction. The source rupture process consists of three sub-events, the first oc- curred near the hypocenter and the rest two ruptured along the up-dip direction and broke the sea bed, causing a maximum slip of about 30 m. The large-scale sea bed breakage may account for the tremendous tsunami disaster which resulted in most of the death and missing in this mega earthquake.展开更多
Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists betw...Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists between an anomalous density body and its surrounding rock,the interface recovered by smooth inversion with Tikhonov regularization is not clear,leading to difficulties in the subsequent geological interpretation.In this work,we develop a joint inversion of surface and borehole gravity data using zeroth-order minimum entropy regularization.The method takes advantage of the complementary information from surface and borehole gravity data to enhance the imaging resolution of density bodies.It also produces a focused imaging of bodies through the zeroth-order minimum entropy regularization without requiring a preselection of a proper focusing parameter.We apply the developed joint inversion approach to three diff erent synthetic data sets.Inversion results show that the focusing inversion with the zeroth-order minimum entropy regularization provides a good description of the true spatial extent of anomalous density bodies.Meanwhile,the joint focusing inversion reconstructs a more reliable density model with a relatively high resolution when a density body is passed through by one or more boreholes.展开更多
We use interferometric synthetic aperture radar （InSAR） and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within th...We use interferometric synthetic aperture radar （InSAR） and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within the seismically active zone of southwestern Tibetan Plateau where the east-west extension of the upper crust is observed. Because of limitations in one pair of InSAR data available, there are trade-offs among centroid depth, rupture area and amount of slip. Available seismic data tightly constrain the focal mechanism and centroid depth of the earthquake but not the horizontal location. Together, two complementary data sets can be used to identify the actual fault plane, better constrain the slip model and event location. We first use regional seismic waveform to estimate point source mechanism, then InSAR data is used to obtain better location. Finally, a joint inversion of teleseismic P-waves and InSAR data is performed to obtain a distributed model. Our preferred point source mechanism indicates a seismic moment of ～2.2×10 18 N·m （～M W 6.2）, a fault plane solution of 171° （342 ° ）/42 ° （48 ° ）/-83 ° （-97 ° ）, corresponding to strike/dip/rake, and a depth of 11 km. The fault plane with strike of 171 ？ and dip of 42° is identified as the ruptured fault with the aid of InSAR data. The preferred source model features compact area of slips between depth of 5–11 km and 10 km along strike with maximum slip amplitude of about 1.5 m.展开更多
The M_(W)7.4 Maduo earthquake occurred on 22 May 2021 at 02:04 CST with a large-expansion surface rupture.This earthquake was located in the Bayan Har block at the eastern Tibetan Plateau,where eight earthquakes of M_...The M_(W)7.4 Maduo earthquake occurred on 22 May 2021 at 02:04 CST with a large-expansion surface rupture.This earthquake was located in the Bayan Har block at the eastern Tibetan Plateau,where eight earthquakes of M_(S)>7.0 have occurred in the past 25 years.Here,we combined interferometric synthetic aperture radar,GPS,and teleseismic data to study the coseismic slip distribution,fault geometry,and dynamic source rupture process of the Maduo earthquake.We found that the overall coseismic deformation field of the Maduo earthquake is distributed in the NWW-SEE direction along 285°.There was slight bending at the western end and two branches at the eastern end.The maximum slip is located near the eastern bending area on the northern branch of the fault system.The rupture nucleated on the Jiangcuo fault and propagated approximately 160 km along-strike in both the NWW and SEE directions.The characteristic source rupture process of the Maduo earthquake is similar to that of the 2010 M_(W)6.8 Yushu earthquake,indicating that similar earthquakes with large-expansion surface ruptures and small shallow slip deficits can occur on both the internal fault and boundary fault of the Bayan Har block.展开更多
The western China lies in the convergence zone between Eurasian and Indian plates.It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth.The lithospheric strength is a ...The western China lies in the convergence zone between Eurasian and Indian plates.It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth.The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations.The effective elastic thickness(T_(e))of the lithosphere can be used to address the lithospheric strength.Previous researchers only used one of the admittance or coherence methods to investigate the T_(e) in the western China.Moreover,most of them ignored the internal loads of the lithosphere during the T_(e) calculation,which can produce large biases in the T_(e) estimations.To provide more reliable T_(e) estimations,we used a new joint inversion method that integrated both admittance and coherence techniques to compute the T_(e) in this study,with the WGM2012 gravity data,the ETOPO1 topographic data,and the Moho depths from the CRUST1.0 model.The internal loads are considered and investigated using the load ratio(F).Our results show that the joint inversion method can yield reliable T_(e) and F values.Based on the analysis of T_(e) and F distributions,we suggest(1)the northern Tibetan Plateau could be the front edge of the plate collision of Eurasian and Indian plates;(2)the southern and part of central Tibetan Plateau have a strong lithospheric mantle related to the rigid underthrusting Indian plate;(3)the southeastern Tibetan Plateau may be experiencing the delamination of lithosphere and upwelling of asthenosphere.展开更多
Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-refl...Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-reflection result. Based on the data of complete Bouguer gravity anomaly and seismic reflection, we obtained a layered interface structure in deep crust down to Moho. Our study showed that the inversion could reveal the interfaces of strata along the survey profile and the directions of regional faults in two-dimension. From the characteristics of the observed topography of the Moho basement, we tentatively confirmed that the uplift of eastern edge of Qinghai-Tibet plateau was caused by the subduetion of the Indian plate.展开更多
A new 3D velocity model of the crust and upper mantle in the southeastern （SE） margin of the Tibetan plateau was obtained by joint inversion of body- and sur- face-wave data. For the body-wave data, we used 7190 eve...A new 3D velocity model of the crust and upper mantle in the southeastern （SE） margin of the Tibetan plateau was obtained by joint inversion of body- and sur- face-wave data. For the body-wave data, we used 7190 events recorded by 102 stations in the SE margin of the Tibetan plateau. The surface-wave data consist of Rayleigh wave phase velocity dispersion curves obtained from ambient noise cross-correlation analysis recorded by a dense array in the SE margin of the Tibetan plateau. The joint inversion clearly improves the Vs model because it is constrained by both data types. The results show that at around 10 km depth there are two low-velocity anomalies embedded within three high-velocity bodies along the Longmenshan fault system. These high-velocity bodies correspond well with the Precambrian massifs, and the two located to the northeast of 2013 Ms 7.0 Lushan earthquake are associated with high fault slip areas during the 2008 Wenchuan earthquake. The aftershock gap between 2013 Lushan earthquake and 2008 Wenchuan earthquake is associated with low-velocity anomalies, which also acts as a barrier zone for ruptures of two earthquakes. Generally large earthquakes （M 〉 5） in the region occurring from 2008 to 2015 are located around the high-velocity zones, indicating that they may act as asperities for these large earthquakes. Joint inversion results also clearly show that there exist low-velocity or weak zones in the mid-lower crust, which are not evenly distributed beneath the SE margin of Tibetan plateau.展开更多
Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint met...Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint method to simultaneously invert formation shear-wave anisotropy and vertical shear velocity using LWD monopole and dipole dispersion data.Theoretical analysis demonstrates that formation shear-wave anisotropy significantly aff ects the dispersion characteristics of Stoneley and formation flexural waves.The inversion objective function was constructed based on the change in dispersion characteristics and was weighted by the spectra of multipole waves.Numerical results using synthetic examples demonstrate that the joint inversion method can not only alleviate the non-uniqueness problem but also help improve the accuracy of the inversion results.The comparison of diff erent signal-to-noise ratio inversion results proved that the weighted inversion method is more accurate and stable.展开更多
Different geophysical exploration methods have significant differences in terms of exploration depth,especially in frequency domain electromagnetic(EM)exploration.According to the definition of skin depth,this differe...Different geophysical exploration methods have significant differences in terms of exploration depth,especially in frequency domain electromagnetic(EM)exploration.According to the definition of skin depth,this difference will increase with the effective detection frequency of the method.As a result,when performing three-dimensional inversion on single type of EM data,it is not possible to effectively distinguish the subsurface geoelectric structure at the full scale.Therefore,it is necessary to perform joint inversion on different type of EM data.In this paper we combine the magnetotelluric method(MT)with the controlled-source audio-magnetotelluric method(CSAMT)to study the frequency-domain three-dimensional(3D)joint inversions,and we use the unstructured finite-element method to do the forward modeling for them,so that the numerical simulation accuracies of different electromagnetic methods can be satisfied.By combining the two sets of data,we can obtain the sensitivity of the electrical structure at different depths,and depict the full-scale subsurface geoelectric structures.In actual mineral exploration,the 3D joint inversion is more useful for identifying subsurface veins in the shallow part and blind mines in the deep part.It can delineate the morphological distribution of ore bodies more completely and provide reliable EM interpretations to guide the mining of minerals.展开更多
There are abundant igneous gas reservoirs in the South China Sea with significant value of research,and lithology classification,mineral analysis and porosity inversion are important links in reservoir evaluation.Howe...There are abundant igneous gas reservoirs in the South China Sea with significant value of research,and lithology classification,mineral analysis and porosity inversion are important links in reservoir evaluation.However,affected by the diverse lithology,complicated mineral and widespread alteration,conventional logging lithology classification and mineral inversion become considerably difficult.At the same time,owing to the limitation of the wireline log response equation,the quantity and accuracy of minerals can hardly meet the exploration requirements of igneous formations.To overcome those issues,this study takes the South China Sea as an example,and combines multi-scale data such as micro rock slices,petrophysical experiments,wireline log and element cutting log to establish a set of joint inversion methods for minerals and porosity of altered igneous rocks.Specifically,we define the lithology and mineral characteristics through core slices and mineral data,and establish an igneous multi-mineral volumetric model.Then we determine element cutting log correction method based on core element data,and combine wireline log and corrected element cutting log to perform the lithology classification and joint inversion of minerals and porosity.However,it is always difficult to determine the elemental eigenvalues of different minerals in inversion.This paper uses multiple linear regression methods to solve this problem.Finally,an integrated inversion technique for altered igneous formations was developed.The results show that the corrected element cutting log are in good agreement with the core element data,and the mineral and porosity results obtained from the joint inversion based on the wireline log and corrected element cutting log are also in good agreement with the core data from X-ray diffraction.The results demonstrate that the inversion technique is applicable and this study provides a new direction for the mineral inversion research of altered igneous formations.展开更多
Multi-component seismic exploration is an important technique in the utilization of P-waves and converted S-waves for oil and gas exploration.It has unique advantages in the structural imaging of gas zones,reservoir p...Multi-component seismic exploration is an important technique in the utilization of P-waves and converted S-waves for oil and gas exploration.It has unique advantages in the structural imaging of gas zones,reservoir prediction,lithology,and gas-water identifi cation,and the development direction and degree of fractures.Multi-component joint inversion is one of the most important steps in multi-component exploration.In this paper,starting from the basic principle of multi-component joint inversion,the diff erences between the method and single P-wave inversion are introduced.Next,the technique is applied to the PLN area of the Sichuan Basin,and the P-wave impedance,S-wave impedance,and density are obtained based on multi-component joint inversion.Through the velocity and lithology,porosity,and gas saturation fi tting formulas,prediction results are calculated,and the results are analyzed.Finally,multi-component joint inversion and single P-wave inversion are compared in eff ective reservoir prediction.The results show that multi-component joint inversion increases the constraints on the inversion conditions,reduces the multi-solution of a single P-wave inversion,and is more objective and reliable for the identification of reservoirs,effectively improving the accuracy of oil and gas reservoir prediction and development.展开更多
This paper first establishes the prior globe dynamical model by geophysics,which is a solid earth elastic deformation model.Then,the parameters of the globe dynamic model can be obtained by inverting the geodetic data...This paper first establishes the prior globe dynamical model by geophysics,which is a solid earth elastic deformation model.Then,the parameters of the globe dynamic model can be obtained by inverting the geodetic data.The inverse method can be used in seismology and geology,and to make earthquake prediction.展开更多
The gravity and magnetic data can be adopted to interpret the internal structure of the Earth.To improve the calculation efficiency during the inversion process and the accuracy and reliability of the reconstructed ph...The gravity and magnetic data can be adopted to interpret the internal structure of the Earth.To improve the calculation efficiency during the inversion process and the accuracy and reliability of the reconstructed physical property models,the triple strategy is adopted in this paper to develop a fast cross-gradient joint inversion for gravity and magnetic data.The cross-gradient constraint contains solving the gradients of the physical property models and performing the cross-product calculation of their gradients.The sparse matrices are first obtained by calculating the gradients of the physical property models derived from the first-order finite difference.Then,the triple method is applied to optimize the storages and the calculations related to the gradients of the physical property models.Therefore,the storage compression amount of the calculations related to the gradients of the physical property models and the cross-gradient constraint are reduced to one-fold of the number of grid cells at least,and the compression ratio increases with the increase of the number of grid cells.The test results from the synthetic data and field data prove that the structural coupling is achieved by using the fast cross-gradient joint inversion method to effectively reduce the multiplicity of solutions and improve the computing efficiency.展开更多
On September 16,2021,a MS6.0 earthquake struck Luxian County,one of the shale gas blocks in the Southeastern Sichuan Basin,China.To understand the seismogenic environment and its mechanism,we inverted a fine three-dim...On September 16,2021,a MS6.0 earthquake struck Luxian County,one of the shale gas blocks in the Southeastern Sichuan Basin,China.To understand the seismogenic environment and its mechanism,we inverted a fine three-dimensional S-wave velocity model from ambient noise tomography using data from a newly deployed dense seismic array around the epicenter,by extracting and jointly inverting the Rayleigh phase and group velocities in the period of 1.6–7.2 s.The results showed that the velocity model varied significantly beneath different geological units.The Yujiasi syncline is characterized by low velocity at depths of~3.0–4.0 km,corresponding to the stable sedimentary layer in the Sichuan Basin.The eastern and western branches of the Huayingshan fault belt generally exhibit high velocities in the NE-SW direction,with a few local low-velocity zones.The Luxian MS6.0 earthquake epicenter is located at the boundary between the high-and low-velocity zones,and the earthquake sequences expand eastward from the epicenter at depths of 3.0–5.0 km.Integrated with the velocity variations around the epicenter,distribution of aftershock sequences,and focal mechanism solution,it is speculated that the seismogenic mechanism of the main shock might be interpreted as the reactivation of pre-existing faults by hydraulic fracturing.展开更多
基金the sponsorship of National Natural Science Foundation of China(42325403)Deep Earth Probe and Mineral Resources Exploration-National Science and Technology Major Project of China(2024ZD1004201)。
文摘Subsurface reservoirs commonly exhibit layered structures.Conventional amplitude variation with angle(AVA)inversion,which relies on the Zoeppritz equation and its approximations,often fails to accurately estimate elastic parameters because it assumes single-interface models and ignores multiple reflections and transmission losses.To address these limitations,this study proposes a novel prestack time-frequency domain joint inversion method that utilizes the reflection matrix method(RMM)as the forward operator.The RMM accurately simulates wave propagation in layered media,while the joint inversion framework minimizes the misfit between observed and synthetic data in both the time and frequency domains.By incorporating Bayesian theory to optimize the inversion process,the method effectively balances contributions from both time-domain waveforms and frequency-domain spectral information through a weighting factor.Tests on both synthetic data and field data demonstrate that the proposed method outperforms conventional AVA inversion and time-domain waveform inversion in accuracy and robustness.Furthermore,the method demonstrates good robustness against variations in initial models,random noise,and coherent noise interference.This study provides a practical and effective approach for high-precision reservoir characterization,with potential applications in complex layered media.
基金funded by the National Natural Science Foundation of China under Grant 42230101the National Agency for Research and Development of Chile(ANID)by Projects AFB180004 and AFB220002the ANID Programa de Cooperación Internacional(PCI)Grant PII-180003.
文摘The Chilean Pampean flat slab subduction segment is characterized by the nearly horizontal subduction of the Nazca Plate within the depth range of 100-120 km.Numerous seismic tomography studies have been conducted to investigate its velocity structure;however,they have used only seismic body wave data or surface wave data.As a result,the existing velocity models in the region may have relatively large uncertainties.In this study,we use body wave arrival times from earthquakes occurring in central Chile between 2014 and 2019,as well as Rayleigh wave phase velocity maps at periods of 5-80 s from ambient noise empirical Green’s functions in Chile.By jointly using body wave arrival times and surface wave dispersion data,we refine the VS model and improve earthquake locations in the central Chile subduction zone.Compared with previous velocity models,our velocity model better reveals an eastward-dipping high-velocity plate representing the subducting Nazca Plate,which is 40-50 km thick and is more consistent with the slab thickness estimated by receiver function imaging and thermal modeling.Overall,the intraslab seismicity distribution spatially correlates well with the slab high-velocity anomalies except along the subduction paths of the CopiapóRidge and Juan Fernández Ridge.Additionally,parallel low-velocity stripes are imaged beneath the subducting plate,which are likely associated with the accumulated melts.The joint inversion velocity model also resolves widespread low-velocity anomalies in the crust beneath the Central Volcanic Zone of the central Andes,likely representing crustal magma chambers for various volcanoes.
基金Supported by the National Natural Science Foundation of China(Grant No.40674063)National Hi-tech Research and Development Program of China(863Program)(Grant No.2006AA09Z311)
文摘Based on the synchronous joint gravity and magnetic inversion of single interface by Pilkington and the need of revealing Cenozoic and crystalline basement thickness in the new round of oil-gas exploration, we propose a joint gravity and magnetic inversion methodfor two-layer models by concentrating on the relationship between the change of thicknessI and position of the middle layer and anomaly and discuss the effects of the key parameters. Model tests and application to field data show the validity of this method.
基金supported by the Natural Science Foundation of China (Grant Nos 40974066 and 40821062)the National Basic Research Program of China (Grant No. 2007CB209602)
文摘Multi-component exploration has many advantages over ordinary P-wave exploration. PP/PS joint AVO analysis and inversion are useful and powerful methods to discriminate between reservoir and non-productive lithology. In this paper, we derive a new PS-wave reflection coefficient approximation equation which is more accurate at larger incidence angles. The equation is simplified for small incidence angles, which makes AVO analysis clearer and easier for angles less than 30 degrees. Based on this approximation, a PP/PS joint inversion is introduced. A real data example shows that oil sands, brine sands and shales can be differentiated based on the P- to S-wave velocity ratio from the PP/PS joint inversion. Fluid factors and Poisson＇s ratio also indicate an anomaly in the target zone at the oil well location.
基金supported by the National Earthquake Science Experiment in Sichuan and Yunnan Provinces of China(#2016 CESE 0201)National Natural Science Foundation of China(#41574034)China National Special Fund for Earthquake Scientific Research in Public Interest(#201508008)
文摘Accurate determination of seismic velocity of the crust is important for understanding regional tectonics and crustal evolution of the Earth. We propose a stepwise joint linearized inversion method using surface wave dispersion, Rayleigh wave ZH ratio （i.e., ellipticity）, and receiver function data to better resolve 1D crustal shear wave velocity （Vs） structure. Surface wave dispersion and Rayleigh wave ZH ratio data are more sensitive to absolute variations of shear wave speed at depths, but their sensi- tivity kernels to shear wave speeds are different and complimentary. However, receiver function data are more sensitive to sharp velocity contrast （e.g., due to the existence of crustal interfaces） and Vp/Vs ratios. The stepwise inversion method takes advantages of the complementary sensitivities of each dataset to better constrain the Vs model in the crust. We firstly invert surface wave dispersion and ZH ratio data to obtain a 1D smooth absolute vs model and then incorporate receiver function data in the joint inver- sion to obtain a finer Vs model with better constraints on interface structures. Through synthetic tests, Monte Carlo error analyses, and application to real data, we demonstrate that the proposed joint inversion method can resolve robust crustal Vs structures and with little initial model dependency.
基金jointly sponsored by the Fundamental Research Funds for the Central Universitiesthe National Natural Science Foundation of China(No.41374078)
文摘A two-dimensional forward and backward algorithm for the controlled-source audio-frequency magnetotelluric （CSAMT） method is developed to invert data in the entire region （near, transition, and far） and deal with the effects of artificial sources. First, a regularization factor is introduced in the 2D magnetic inversion, and the magnetic susceptibility is updated in logarithmic form so that the inversion magnetic susceptibility is always positive. Second, the joint inversion of the CSAMT and magnetic methods is completed with the introduction of the cross gradient. By searching for the weight of the cross-gradient term in the objective function, the mutual influence between two different physical properties at different locations are avoided. Model tests show that the joint inversion based on cross-gradient theory offers better results than the single-method inversion. The 2D forward and inverse algorithm for CSAMT with source can effectively deal with artificial sources and ensures the reliability of the final joint inversion algorithm.
基金financially supported by the National Natural Science Foundation of China (Nos. 90915012 and 41090291)the Research Project in Earthquake Science, CEA (No.201108002)
文摘Teleseismic and GPS data were jointly inverted for the rupture process of the 2011 Tohoku earthquake. The inversion results show that it is a bilateral rupture event with an average rupture velocity less than 2.0 km/s along the fault strike direction. The source rupture process consists of three sub-events, the first oc- curred near the hypocenter and the rest two ruptured along the up-dip direction and broke the sea bed, causing a maximum slip of about 30 m. The large-scale sea bed breakage may account for the tremendous tsunami disaster which resulted in most of the death and missing in this mega earthquake.
基金financially supported by the National Key Research and Development Program of China(no.2018YFC0603300)the National Natural Science Foundation of China(no.42004054)。
文摘Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists between an anomalous density body and its surrounding rock,the interface recovered by smooth inversion with Tikhonov regularization is not clear,leading to difficulties in the subsequent geological interpretation.In this work,we develop a joint inversion of surface and borehole gravity data using zeroth-order minimum entropy regularization.The method takes advantage of the complementary information from surface and borehole gravity data to enhance the imaging resolution of density bodies.It also produces a focused imaging of bodies through the zeroth-order minimum entropy regularization without requiring a preselection of a proper focusing parameter.We apply the developed joint inversion approach to three diff erent synthetic data sets.Inversion results show that the focusing inversion with the zeroth-order minimum entropy regularization provides a good description of the true spatial extent of anomalous density bodies.Meanwhile,the joint focusing inversion reconstructs a more reliable density model with a relatively high resolution when a density body is passed through by one or more boreholes.
基金study was supported jointly by National Natural Science Foundation of China (Nos.40821160549 and 41074032)CAS Knowledge Innovation Program (No. KZCX2-YW-116-1)Joint Seismological Science Fundation of China(Nos.200808078 and 200708035)
文摘We use interferometric synthetic aperture radar （InSAR） and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within the seismically active zone of southwestern Tibetan Plateau where the east-west extension of the upper crust is observed. Because of limitations in one pair of InSAR data available, there are trade-offs among centroid depth, rupture area and amount of slip. Available seismic data tightly constrain the focal mechanism and centroid depth of the earthquake but not the horizontal location. Together, two complementary data sets can be used to identify the actual fault plane, better constrain the slip model and event location. We first use regional seismic waveform to estimate point source mechanism, then InSAR data is used to obtain better location. Finally, a joint inversion of teleseismic P-waves and InSAR data is performed to obtain a distributed model. Our preferred point source mechanism indicates a seismic moment of ～2.2×10 18 N·m （～M W 6.2）, a fault plane solution of 171° （342 ° ）/42 ° （48 ° ）/-83 ° （-97 ° ）, corresponding to strike/dip/rake, and a depth of 11 km. The fault plane with strike of 171 ？ and dip of 42° is identified as the ruptured fault with the aid of InSAR data. The preferred source model features compact area of slips between depth of 5–11 km and 10 km along strike with maximum slip amplitude of about 1.5 m.
基金supported by grants of the K.C.Wong Education Foundation(No.GJTD-2019-04)Second Tibetan Plateau Scientific Expedition and Research Program(No.2019QZKK07)National Nature Science Foundation of China(No.41988101-0104)。
文摘The M_(W)7.4 Maduo earthquake occurred on 22 May 2021 at 02:04 CST with a large-expansion surface rupture.This earthquake was located in the Bayan Har block at the eastern Tibetan Plateau,where eight earthquakes of M_(S)>7.0 have occurred in the past 25 years.Here,we combined interferometric synthetic aperture radar,GPS,and teleseismic data to study the coseismic slip distribution,fault geometry,and dynamic source rupture process of the Maduo earthquake.We found that the overall coseismic deformation field of the Maduo earthquake is distributed in the NWW-SEE direction along 285°.There was slight bending at the western end and two branches at the eastern end.The maximum slip is located near the eastern bending area on the northern branch of the fault system.The rupture nucleated on the Jiangcuo fault and propagated approximately 160 km along-strike in both the NWW and SEE directions.The characteristic source rupture process of the Maduo earthquake is similar to that of the 2010 M_(W)6.8 Yushu earthquake,indicating that similar earthquakes with large-expansion surface ruptures and small shallow slip deficits can occur on both the internal fault and boundary fault of the Bayan Har block.
基金This work is supported by the Special Fund of the Institute of GeophysicsChina Earthquake Administration(No.DQJB20K31)+2 种基金the National Key R&D Program of China(Nos.2018YFC0603502 and2017YFC1500503)the National Natural Science Foundation of China(Nos.41774090 and U1939205)financial support by China Postdoctoral Science Foundation(No.2018M641424)。
文摘The western China lies in the convergence zone between Eurasian and Indian plates.It is an ideal place to study the lithosphere dynamics and tectonic evolutions on the continental Earth.The lithospheric strength is a key factor in controlling the lithosphere dynamics and deformations.The effective elastic thickness(T_(e))of the lithosphere can be used to address the lithospheric strength.Previous researchers only used one of the admittance or coherence methods to investigate the T_(e) in the western China.Moreover,most of them ignored the internal loads of the lithosphere during the T_(e) calculation,which can produce large biases in the T_(e) estimations.To provide more reliable T_(e) estimations,we used a new joint inversion method that integrated both admittance and coherence techniques to compute the T_(e) in this study,with the WGM2012 gravity data,the ETOPO1 topographic data,and the Moho depths from the CRUST1.0 model.The internal loads are considered and investigated using the load ratio(F).Our results show that the joint inversion method can yield reliable T_(e) and F values.Based on the analysis of T_(e) and F distributions,we suggest(1)the northern Tibetan Plateau could be the front edge of the plate collision of Eurasian and Indian plates;(2)the southern and part of central Tibetan Plateau have a strong lithospheric mantle related to the rigid underthrusting Indian plate;(3)the southeastern Tibetan Plateau may be experiencing the delamination of lithosphere and upwelling of asthenosphere.
基金supported by the Key Foundation of Institute of Seismology,China Earthquake Administration( IS200916004)
文摘Yushu Ms7.1 earthquake occurred on the Ganzi-Yushu fault zone, across which we carried out a joint relative-gravity and seismic-reflection survey, and then performed a gravity inversion constrained by the seismic-reflection result. Based on the data of complete Bouguer gravity anomaly and seismic reflection, we obtained a layered interface structure in deep crust down to Moho. Our study showed that the inversion could reveal the interfaces of strata along the survey profile and the directions of regional faults in two-dimension. From the characteristics of the observed topography of the Moho basement, we tentatively confirmed that the uplift of eastern edge of Qinghai-Tibet plateau was caused by the subduetion of the Indian plate.
基金supported by the Natural National Science Foundation of China under grant number 41474039China National Special Fund for Earthquake Scientific Research in Public Interest under grant number 2016 CESE 0201+1 种基金Shanghai Committee of Science and Technology under grant number 14231202600the Fundamental Research Funds for the Central Universities under grant number WK2080000053
文摘A new 3D velocity model of the crust and upper mantle in the southeastern （SE） margin of the Tibetan plateau was obtained by joint inversion of body- and sur- face-wave data. For the body-wave data, we used 7190 events recorded by 102 stations in the SE margin of the Tibetan plateau. The surface-wave data consist of Rayleigh wave phase velocity dispersion curves obtained from ambient noise cross-correlation analysis recorded by a dense array in the SE margin of the Tibetan plateau. The joint inversion clearly improves the Vs model because it is constrained by both data types. The results show that at around 10 km depth there are two low-velocity anomalies embedded within three high-velocity bodies along the Longmenshan fault system. These high-velocity bodies correspond well with the Precambrian massifs, and the two located to the northeast of 2013 Ms 7.0 Lushan earthquake are associated with high fault slip areas during the 2008 Wenchuan earthquake. The aftershock gap between 2013 Lushan earthquake and 2008 Wenchuan earthquake is associated with low-velocity anomalies, which also acts as a barrier zone for ruptures of two earthquakes. Generally large earthquakes （M 〉 5） in the region occurring from 2008 to 2015 are located around the high-velocity zones, indicating that they may act as asperities for these large earthquakes. Joint inversion results also clearly show that there exist low-velocity or weak zones in the mid-lower crust, which are not evenly distributed beneath the SE margin of Tibetan plateau.
基金supported by the National Natural Science Foundation of China (Grant No.12174421)the Hubei Key Laboratory of Advanced Aerospace Propulsion Technology (Grant No.KFJJ2020-02).
文摘Most sedimentary formations with fine layers can be characterized as transversely isotropic media.The evaluation of shear-wave anisotropy is critical in logging-while-drilling(LWD)applications.We developed a joint method to simultaneously invert formation shear-wave anisotropy and vertical shear velocity using LWD monopole and dipole dispersion data.Theoretical analysis demonstrates that formation shear-wave anisotropy significantly aff ects the dispersion characteristics of Stoneley and formation flexural waves.The inversion objective function was constructed based on the change in dispersion characteristics and was weighted by the spectra of multipole waves.Numerical results using synthetic examples demonstrate that the joint inversion method can not only alleviate the non-uniqueness problem but also help improve the accuracy of the inversion results.The comparison of diff erent signal-to-noise ratio inversion results proved that the weighted inversion method is more accurate and stable.
基金Supported by the National Natural Science Foundation of China(No.42074120).
文摘Different geophysical exploration methods have significant differences in terms of exploration depth,especially in frequency domain electromagnetic(EM)exploration.According to the definition of skin depth,this difference will increase with the effective detection frequency of the method.As a result,when performing three-dimensional inversion on single type of EM data,it is not possible to effectively distinguish the subsurface geoelectric structure at the full scale.Therefore,it is necessary to perform joint inversion on different type of EM data.In this paper we combine the magnetotelluric method(MT)with the controlled-source audio-magnetotelluric method(CSAMT)to study the frequency-domain three-dimensional(3D)joint inversions,and we use the unstructured finite-element method to do the forward modeling for them,so that the numerical simulation accuracies of different electromagnetic methods can be satisfied.By combining the two sets of data,we can obtain the sensitivity of the electrical structure at different depths,and depict the full-scale subsurface geoelectric structures.In actual mineral exploration,the 3D joint inversion is more useful for identifying subsurface veins in the shallow part and blind mines in the deep part.It can delineate the morphological distribution of ore bodies more completely and provide reliable EM interpretations to guide the mining of minerals.
基金The project was supported by the National Natural Science Foundation of China(Grant No.42204122).
文摘There are abundant igneous gas reservoirs in the South China Sea with significant value of research,and lithology classification,mineral analysis and porosity inversion are important links in reservoir evaluation.However,affected by the diverse lithology,complicated mineral and widespread alteration,conventional logging lithology classification and mineral inversion become considerably difficult.At the same time,owing to the limitation of the wireline log response equation,the quantity and accuracy of minerals can hardly meet the exploration requirements of igneous formations.To overcome those issues,this study takes the South China Sea as an example,and combines multi-scale data such as micro rock slices,petrophysical experiments,wireline log and element cutting log to establish a set of joint inversion methods for minerals and porosity of altered igneous rocks.Specifically,we define the lithology and mineral characteristics through core slices and mineral data,and establish an igneous multi-mineral volumetric model.Then we determine element cutting log correction method based on core element data,and combine wireline log and corrected element cutting log to perform the lithology classification and joint inversion of minerals and porosity.However,it is always difficult to determine the elemental eigenvalues of different minerals in inversion.This paper uses multiple linear regression methods to solve this problem.Finally,an integrated inversion technique for altered igneous formations was developed.The results show that the corrected element cutting log are in good agreement with the core element data,and the mineral and porosity results obtained from the joint inversion based on the wireline log and corrected element cutting log are also in good agreement with the core data from X-ray diffraction.The results demonstrate that the inversion technique is applicable and this study provides a new direction for the mineral inversion research of altered igneous formations.
基金This work was supported by“Thirteenth Five-Year”national science and technology major Project(No.2017ZX05018005-004)CNPC fundamental research project(No.2016E-0604)National Natural Science Foundation of China(No.41374111).
文摘Multi-component seismic exploration is an important technique in the utilization of P-waves and converted S-waves for oil and gas exploration.It has unique advantages in the structural imaging of gas zones,reservoir prediction,lithology,and gas-water identifi cation,and the development direction and degree of fractures.Multi-component joint inversion is one of the most important steps in multi-component exploration.In this paper,starting from the basic principle of multi-component joint inversion,the diff erences between the method and single P-wave inversion are introduced.Next,the technique is applied to the PLN area of the Sichuan Basin,and the P-wave impedance,S-wave impedance,and density are obtained based on multi-component joint inversion.Through the velocity and lithology,porosity,and gas saturation fi tting formulas,prediction results are calculated,and the results are analyzed.Finally,multi-component joint inversion and single P-wave inversion are compared in eff ective reservoir prediction.The results show that multi-component joint inversion increases the constraints on the inversion conditions,reduces the multi-solution of a single P-wave inversion,and is more objective and reliable for the identification of reservoirs,effectively improving the accuracy of oil and gas reservoir prediction and development.
文摘This paper first establishes the prior globe dynamical model by geophysics,which is a solid earth elastic deformation model.Then,the parameters of the globe dynamic model can be obtained by inverting the geodetic data.The inverse method can be used in seismology and geology,and to make earthquake prediction.
基金supported by the National Key Research and Development Program(Grant No.2021YFA0716100)the National Key Research and Development Program of China Project(Grant No.2018YFC0603502)Henan Youth Science Fund Program(Grant No.212300410105).
文摘The gravity and magnetic data can be adopted to interpret the internal structure of the Earth.To improve the calculation efficiency during the inversion process and the accuracy and reliability of the reconstructed physical property models,the triple strategy is adopted in this paper to develop a fast cross-gradient joint inversion for gravity and magnetic data.The cross-gradient constraint contains solving the gradients of the physical property models and performing the cross-product calculation of their gradients.The sparse matrices are first obtained by calculating the gradients of the physical property models derived from the first-order finite difference.Then,the triple method is applied to optimize the storages and the calculations related to the gradients of the physical property models.Therefore,the storage compression amount of the calculations related to the gradients of the physical property models and the cross-gradient constraint are reduced to one-fold of the number of grid cells at least,and the compression ratio increases with the increase of the number of grid cells.The test results from the synthetic data and field data prove that the structural coupling is achieved by using the fast cross-gradient joint inversion method to effectively reduce the multiplicity of solutions and improve the computing efficiency.
基金This work was supported by the Special Fund of the Institute of Geophysics,China Earthquake Administration(Nos.DQJB22B19,DQJB22R29 and DQJB22B26)the National Natural Science Foundation of China(Nos.41974066,U1839209 and 42074053)。
文摘On September 16,2021,a MS6.0 earthquake struck Luxian County,one of the shale gas blocks in the Southeastern Sichuan Basin,China.To understand the seismogenic environment and its mechanism,we inverted a fine three-dimensional S-wave velocity model from ambient noise tomography using data from a newly deployed dense seismic array around the epicenter,by extracting and jointly inverting the Rayleigh phase and group velocities in the period of 1.6–7.2 s.The results showed that the velocity model varied significantly beneath different geological units.The Yujiasi syncline is characterized by low velocity at depths of~3.0–4.0 km,corresponding to the stable sedimentary layer in the Sichuan Basin.The eastern and western branches of the Huayingshan fault belt generally exhibit high velocities in the NE-SW direction,with a few local low-velocity zones.The Luxian MS6.0 earthquake epicenter is located at the boundary between the high-and low-velocity zones,and the earthquake sequences expand eastward from the epicenter at depths of 3.0–5.0 km.Integrated with the velocity variations around the epicenter,distribution of aftershock sequences,and focal mechanism solution,it is speculated that the seismogenic mechanism of the main shock might be interpreted as the reactivation of pre-existing faults by hydraulic fracturing.
