Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps,such as lateaggradational lowstands prograding wedge systems(LPWS)within lowstands systems tra...Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps,such as lateaggradational lowstands prograding wedge systems(LPWS)within lowstands systems tracts(LST).However,seismic data acquisition operations are always dominated by exceptional seismic coherent noise events,e.g.,multiples,which reduce the signal strengths of the sourcegenerated incident seismic waves within vertically and laterally heterogeneous earth systems.Hence,these noise events create hurdles in predicting paleo-depositional impedance(PDI),paleo-thickness(PTS),paleo-dense fractured networks,erosional and depositional zones,faultcontrolled migrations,and types of seismic reflection configurations(SRFC),which are key elements in developing stratigraphic pinch-out traps.This research utilizes the state-of-the-art technologies of spectral wavelet-based instantaneous time-frequency analysis and seismic waveform frequency-controlled porosity-constrained static reservoir simulation(FDPVS)tools to quantify the LPWS inside the Onshore Basin,Pakistan.The use of conventional amplitude-based seismic attributes,such as the average energy,remained a better tool for deciphering the overall geological architecture of the LPWS.Conventional FDPVS realizations resolved a PDI of−1.391 gm./c.c.^(*)m/s to−0.97 gm./c.c.^(*)m/s for LPWS with PTS of 12 and 20 m,respectively.A 0.9 km lateral extent of paleo-dense fractured networks(PDFN)with a strong linear regression R^(2)=0.93 was also resolved.Average energy attribute-based instantaneous frequency FDPVS realizations enabled the imaging of parallel-toprograding SRFC with resolved magnitudes of−0.259 gm./c.c.^(*)m/s for PDI,20 m for PTS,and 0.73 km for PDFN with linear regression transforms at R^(2)=0.92,which indicates the deposition of onlap fill facies inside the LPWS during extensive sea-level fall.These realizations have also resolved frequency-controlled fault migrations on 27-Hz spectral waveform-based amplitude plots with 2.174 gm./c.c.^(*)m/s PDI for conduit fault systems and 27-Hz with 0.585 gm./c.c.^(*)m/s PDI for sealing fault systems.All these structural configurations are completely sealed up by transgressive seals of transgressive systems tracts and,hence,developed into pure stratigraphic-based oil and gas plays.This research has strong implications for side-tracking drilling locations and provides an analogue for basins with similar geology and stratigraphy worldwide.展开更多
Waveforms of artificially induced explosions and collapse events recorded by the seismic network share similarities with natural earthquakes.Failure to identify and screen them in a timely manner can introduce confusi...Waveforms of artificially induced explosions and collapse events recorded by the seismic network share similarities with natural earthquakes.Failure to identify and screen them in a timely manner can introduce confusion into the earthquake catalog established using these recordings,thereby impacting future seismological research.Therefore,the identification and separation of natural earthquakes from continuous seismic signals contribute to the monitoring and early warning of destructive tectonic earthquakes.A 1D convolutional neural network(CNN)is proposed for seismic event classification using an efficient channel attention mechanism and an improved light inception block.A total of 9937 seismic sample records are obtained after waveform interception,filtering,and normalization.The proposed model can obtain better classification performance than other major existing methods,exhibiting 96.79%overall classification accuracy and 96.73%,94.85%,and 96.35%classification accuracy for natural seismic events,collapse events,and blasting events,respectively.Meanwhile,the proposed model is lighter than the 2D convolutional and common inception networks.We also apply the proposed model to the seismic data recorded at the University of Utah seismograph stations and compare its performance with that of the CNN-waveform model.展开更多
Seismic waveform clustering is a useful technique for lithologic identification and reservoir characterization.The current seismic waveform clustering algorithms are predominantly based on a fixed time window,which is...Seismic waveform clustering is a useful technique for lithologic identification and reservoir characterization.The current seismic waveform clustering algorithms are predominantly based on a fixed time window,which is applicable for layers of stable thickness.When a layer exhibits variable thickness in the seismic response,a fixed time window cannot provide comprehensive geologic information for the target interval.Therefore,we propose a novel approach for a waveform clustering workfl ow based on a variable time window to enable broader applications.The dynamic time warping(DTW)distance is fi rst introduced to effectively measure the similarities between seismic waveforms with various lengths.We develop a DTW distance-based clustering algorithm to extract centroids,and we then determine the class of all seismic traces according to the DTW distances from centroids.To greatly reduce the computational complexity in seismic data application,we propose a superpixel-based seismic data thinning approach.We further propose an integrated workfl ow that can be applied to practical seismic data by incorporating the DTW distance-based clustering and seismic data thinning algorithms.We evaluated the performance by applying the proposed workfl ow to synthetic seismograms and seismic survey data.Compared with the the traditional waveform clustering method,the synthetic seismogram results demonstrate the enhanced capability of the proposed workfl ow to detect boundaries of diff erent lithologies or lithologic associations with variable thickness.Results from a practical application show that the planar map of seismic waveform clustering obtained by the proposed workfl ow correlates well with the geological characteristics of wells in terms of reservoir thickness.展开更多
Under the condition of thin interbeds with great lateral changes in terrestrial basins,a seismic meme inversion method is established based on the analysis of seismic sedimentology technology.The relationship between ...Under the condition of thin interbeds with great lateral changes in terrestrial basins,a seismic meme inversion method is established based on the analysis of seismic sedimentology technology.The relationship between seismic waveform and high-frequency well logs is established through dynamic clustering of seismic waveform to improve the vertical and horizontal resolution of inversion results;meanwhile,by constructing the Bayesian inversion framework of different seismic facies,the real facies controlled inversion is realized.The forward model verification results show that the seismic meme inversion can realize precise prediction of 3 m thick thin interbeds,proving the rationality and high precision of the method.The application in the Daqing placanticline shows that the seismic meme inversion could identify 2 m thin interbeds,and the coincidence rates of inversion results and drilling data were more than 80%.The seismic meme inversion method can improve the accuracy of reservoir prediction and provides a useful mean for thin interbeds prediction in terrestrial basins.展开更多
The firework algorithm（FWA） is a novel swarm intelligence-based method recently proposed for the optimization of multi-parameter, nonlinear functions. Numerical waveform inversion experiments using a synthetic model...The firework algorithm（FWA） is a novel swarm intelligence-based method recently proposed for the optimization of multi-parameter, nonlinear functions. Numerical waveform inversion experiments using a synthetic model show that the FWA performs well in both solution quality and efficiency. We apply the FWA in this study to crustal velocity structure inversion using regional seismic waveform data of central Gansu on the northeastern margin of the Qinghai-Tibet plateau. Seismograms recorded from the moment magnitude（MW） 5.4 Minxian earthquake enable obtaining an average crustal velocity model for this region. We initially carried out a series of FWA robustness tests in regional waveform inversion at the same earthquake and station positions across the study region,inverting two velocity structure models, with and without a low-velocity crustal layer; the accuracy of our average inversion results and their standard deviations reveal the advantages of the FWA for the inversion of regional seismic waveforms. We applied the FWA across our study area using three component waveform data recorded by nine broadband permanent seismic stations with epicentral distances ranging between 146 and 437 km. These inversion results show that the average thickness of the crust in this region is 46.75 km, while thicknesses of the sedimentary layer, and the upper, middle, and lower crust are 3.15,15.69, 13.08, and 14.83 km, respectively. Results also show that the P-wave velocities of these layers and the upper mantle are 4.47, 6.07, 6.12, 6.87, and 8.18 km/s,respectively.展开更多
An algorithm for detecting low-frequency seismic events is developed and applied to the detection of low-frequency events before the 2008 Wenchuan and the 2013 Lushan earthquakes. Continuous vertical-component wavefor...An algorithm for detecting low-frequency seismic events is developed and applied to the detection of low-frequency events before the 2008 Wenchuan and the 2013 Lushan earthquakes. Continuous vertical-component waveforms of some broadband stations in the few months before the Wenchuan and Lushan earthquakes are processed by applying a bandpass filter in 2- 8Hz,and then converted to envelopes with a smoothing time of 10 s window and a median filter with a 20 min window. As a result,teleseismic,long-period noise and local small earthquakes are removed,the filtered amplitude is obviously larger than that of the noise and lasts for a dozen minutes to several hours during a few days in a few stations before the Wenchuan and Lushan earthquakes,respectively. The waveform and envelope are similar to that of a non-volcanic tremor( NVT). There are suspected NVT before the two earthquakes. Preliminary application demonstrates that this algorithm is potentially useful for extracting NVT signals from continuous seismic waveforms.展开更多
Taking the fluvial reservoir of the Neogene Minghuazhen Formation in Bozhong S oilfield in China as an example, a detailed study of the interlayer in the reservoir was conducted. From the perspective of sedimentary ge...Taking the fluvial reservoir of the Neogene Minghuazhen Formation in Bozhong S oilfield in China as an example, a detailed study of the interlayer in the reservoir was conducted. From the perspective of sedimentary genesis of the interlayer, three types of genesis of the interlayer are summarized and analyzed, namely, fine grain sediment in the inter peak channel, suspended sediment in the post flood channel, and abandoned channel sediment. At the same time, combined with seismic waveform analysis, the distribution characteristics and morphology of the interlayer in complex fluvial facies oilfield are carefully depicted, and the horizontal well optimization implementation is guided based on the planar and three-dimensional spatial distribution characteristics of the interlayer. This method enriches the characterization technology of interlayer in offshore oilfields, and has important guiding significance for the overall evaluation and development research of complex fluvial facies oilfields.展开更多
The Jurassic Lianggaoshan Formation in eastern Sichuan Basin is a key target for shale oil exploration.It faces challenges in three-pressure prediction due to complex structural and sedimentary interactions,as well as...The Jurassic Lianggaoshan Formation in eastern Sichuan Basin is a key target for shale oil exploration.It faces challenges in three-pressure prediction due to complex structural and sedimentary interactions,as well as strong reservoir anisotropy.These issues often lead to wellbore instability and gas logging anomalies during drilling.This study presents an integrated workflow that combines residual moveout correction using correlation-based dynamic time warping(CDTW),high-resolution seismic waveform indication inversion,and three-pressure prediction of jointing well-seismic data.Applied to the LT1 well block,the workflow effectively corrects anisotropic residual moveout in image gathers,leading to a signal strength increase of over 10%in frequency bands above 30 Hz and enhancing event continuity.High-resolution rock mechanical parameters are obtained through seismic waveform inversion and regional calibration,enabling the prediction of three-dimensional pore pressure,collapse pressure and fracture pressure.The results are consistent with actual drilling gas shows and core data,confirming the method's accuracy and supporting mud weight planning and wellbore stability efforts.This cost-effective and technically robust approach proves highly reliable in complex environments with significant heterogeneity and anisotropy,assisting drilling decisions and risk management in eastern Sichuan and similar challenging geological settings.展开更多
The Support Vector Machine （SVM） method can be used to set up a nonlinear function prediction model. It is based on the small sample learning theory. The kernel function can be constructed automatically based on the...The Support Vector Machine （SVM） method can be used to set up a nonlinear function prediction model. It is based on the small sample learning theory. The kernel function can be constructed automatically based on the actual sample data by using the SVM method. As a result, the function not only gets a higher fit precision but is also better generalized. The frequency spectrum and seismic waveform are related by Fourier transform, so they are two different forms of the same physical phenomenon. The variety of waveform character reflects stratigraphic differences and frequency spectrum differences reflect the variation of lithology, fluid composition, and formation thickness. It directly predicts sandstone thickness using the seismic waveform. This not only fully utilizes the seismic information but also greatly increases the accuracy of the prediction. Model examples and actual applications show the applicability of this method.展开更多
The Mw 6.8 Adassil earthquake that occurred in the High Atlas on September 8,2023,was a catastrophic event that provided a rare opportunity to study the mechanics of deep crustal seismicity.This research aimed to deci...The Mw 6.8 Adassil earthquake that occurred in the High Atlas on September 8,2023,was a catastrophic event that provided a rare opportunity to study the mechanics of deep crustal seismicity.This research aimed to decipher the rupture characteristics of the Adassil earthquake by analyzing teleseismic waveform data in conjunction with interferometric synthetic aperture radar(InSAR)observations from both ascending and descending orbits.Our analysis revealed a reverse fault mechanism with a centroid depth of approximately 28 km,exceeding the typical range for crustal earthquakes.This result suggests the presence of cooler temperatures in the lower crust,which facilitates the accumulation of tectonic stress.The earthquake exhibited a steep reverse mechanism,dipping at 70°,accompanied by minor strike-slip motion.Within the geotectonic framework of the High Atlas,known for its volcanic legacy and resulting thermal irregularities,we investigated the potential contributions of these factors to the initiation of the Adassil earthquake.Deep seismicity within the lower crust,away from plate boundaries,calls for extensive research to elucidate its implications for regional seismic hazard assessment.Our findings highlight the critical importance of studying and preparing for significant seismic events in similar geological settings,which would provide valuable insights into regional seismic hazard assessments and geodynamic paradigms.展开更多
Although the Sichuan basin is a stable block with low historical seismicity,the Suining M5.0 earthquake on January31,2010 occurred near the center of the basin,causing casualty and substantial damage.Previous studies ...Although the Sichuan basin is a stable block with low historical seismicity,the Suining M5.0 earthquake on January31,2010 occurred near the center of the basin,causing casualty and substantial damage.Previous studies have shown that the earthquake is very shallow and may occur in the sedimentary cover rocks,but its causative fault has not been identified.Based on local broadband seismic waveform data as well as a pair of ALOS PALSAR ascending orbit data,we explore the seismogenic mechanism via further constraining the source depth and the ruptured fault.The earthquake caused ground uplift in the southeast of the epicenter area,with a maximum line of sight displacement of about 13.6 cm,much larger than the displacement caused by a M5 earthquake at a typical depth of 10 km,which indicates that the earthquake is very shallow.Through joint inversion of seismic waveform and InSAR data,we obtain the moment magnitude of Suining earthquake as MW4.5,with the strike,dip,and rake of its fault plane as 17°,66° and 90°,respectively,and the centroid depth less than 1 km,supporting that the earthquake occurred at the shallow part of a high angle thrust fault dipping to the southeast.It is further confirmed that the earthquake may be triggered by the diffusion of high-pressure fluid migrating from the underside gas reservoir.展开更多
文摘Seismic quantitative reservoir simulations and characterizations have played a vital role in exploring stratigraphic traps,such as lateaggradational lowstands prograding wedge systems(LPWS)within lowstands systems tracts(LST).However,seismic data acquisition operations are always dominated by exceptional seismic coherent noise events,e.g.,multiples,which reduce the signal strengths of the sourcegenerated incident seismic waves within vertically and laterally heterogeneous earth systems.Hence,these noise events create hurdles in predicting paleo-depositional impedance(PDI),paleo-thickness(PTS),paleo-dense fractured networks,erosional and depositional zones,faultcontrolled migrations,and types of seismic reflection configurations(SRFC),which are key elements in developing stratigraphic pinch-out traps.This research utilizes the state-of-the-art technologies of spectral wavelet-based instantaneous time-frequency analysis and seismic waveform frequency-controlled porosity-constrained static reservoir simulation(FDPVS)tools to quantify the LPWS inside the Onshore Basin,Pakistan.The use of conventional amplitude-based seismic attributes,such as the average energy,remained a better tool for deciphering the overall geological architecture of the LPWS.Conventional FDPVS realizations resolved a PDI of−1.391 gm./c.c.^(*)m/s to−0.97 gm./c.c.^(*)m/s for LPWS with PTS of 12 and 20 m,respectively.A 0.9 km lateral extent of paleo-dense fractured networks(PDFN)with a strong linear regression R^(2)=0.93 was also resolved.Average energy attribute-based instantaneous frequency FDPVS realizations enabled the imaging of parallel-toprograding SRFC with resolved magnitudes of−0.259 gm./c.c.^(*)m/s for PDI,20 m for PTS,and 0.73 km for PDFN with linear regression transforms at R^(2)=0.92,which indicates the deposition of onlap fill facies inside the LPWS during extensive sea-level fall.These realizations have also resolved frequency-controlled fault migrations on 27-Hz spectral waveform-based amplitude plots with 2.174 gm./c.c.^(*)m/s PDI for conduit fault systems and 27-Hz with 0.585 gm./c.c.^(*)m/s PDI for sealing fault systems.All these structural configurations are completely sealed up by transgressive seals of transgressive systems tracts and,hence,developed into pure stratigraphic-based oil and gas plays.This research has strong implications for side-tracking drilling locations and provides an analogue for basins with similar geology and stratigraphy worldwide.
基金supported by the Jiangsu Provincial Key R&D Programme 261(BE2020116,BE2022154).
文摘Waveforms of artificially induced explosions and collapse events recorded by the seismic network share similarities with natural earthquakes.Failure to identify and screen them in a timely manner can introduce confusion into the earthquake catalog established using these recordings,thereby impacting future seismological research.Therefore,the identification and separation of natural earthquakes from continuous seismic signals contribute to the monitoring and early warning of destructive tectonic earthquakes.A 1D convolutional neural network(CNN)is proposed for seismic event classification using an efficient channel attention mechanism and an improved light inception block.A total of 9937 seismic sample records are obtained after waveform interception,filtering,and normalization.The proposed model can obtain better classification performance than other major existing methods,exhibiting 96.79%overall classification accuracy and 96.73%,94.85%,and 96.35%classification accuracy for natural seismic events,collapse events,and blasting events,respectively.Meanwhile,the proposed model is lighter than the 2D convolutional and common inception networks.We also apply the proposed model to the seismic data recorded at the University of Utah seismograph stations and compare its performance with that of the CNN-waveform model.
基金supported by the National Science and Technology Major Project (No. 2017ZX05001-003)。
文摘Seismic waveform clustering is a useful technique for lithologic identification and reservoir characterization.The current seismic waveform clustering algorithms are predominantly based on a fixed time window,which is applicable for layers of stable thickness.When a layer exhibits variable thickness in the seismic response,a fixed time window cannot provide comprehensive geologic information for the target interval.Therefore,we propose a novel approach for a waveform clustering workfl ow based on a variable time window to enable broader applications.The dynamic time warping(DTW)distance is fi rst introduced to effectively measure the similarities between seismic waveforms with various lengths.We develop a DTW distance-based clustering algorithm to extract centroids,and we then determine the class of all seismic traces according to the DTW distances from centroids.To greatly reduce the computational complexity in seismic data application,we propose a superpixel-based seismic data thinning approach.We further propose an integrated workfl ow that can be applied to practical seismic data by incorporating the DTW distance-based clustering and seismic data thinning algorithms.We evaluated the performance by applying the proposed workfl ow to synthetic seismograms and seismic survey data.Compared with the the traditional waveform clustering method,the synthetic seismogram results demonstrate the enhanced capability of the proposed workfl ow to detect boundaries of diff erent lithologies or lithologic associations with variable thickness.Results from a practical application show that the planar map of seismic waveform clustering obtained by the proposed workfl ow correlates well with the geological characteristics of wells in terms of reservoir thickness.
文摘Under the condition of thin interbeds with great lateral changes in terrestrial basins,a seismic meme inversion method is established based on the analysis of seismic sedimentology technology.The relationship between seismic waveform and high-frequency well logs is established through dynamic clustering of seismic waveform to improve the vertical and horizontal resolution of inversion results;meanwhile,by constructing the Bayesian inversion framework of different seismic facies,the real facies controlled inversion is realized.The forward model verification results show that the seismic meme inversion can realize precise prediction of 3 m thick thin interbeds,proving the rationality and high precision of the method.The application in the Daqing placanticline shows that the seismic meme inversion could identify 2 m thin interbeds,and the coincidence rates of inversion results and drilling data were more than 80%.The seismic meme inversion method can improve the accuracy of reservoir prediction and provides a useful mean for thin interbeds prediction in terrestrial basins.
基金supported by the National Natural Science Foundation of China (No. 41174034)
文摘The firework algorithm（FWA） is a novel swarm intelligence-based method recently proposed for the optimization of multi-parameter, nonlinear functions. Numerical waveform inversion experiments using a synthetic model show that the FWA performs well in both solution quality and efficiency. We apply the FWA in this study to crustal velocity structure inversion using regional seismic waveform data of central Gansu on the northeastern margin of the Qinghai-Tibet plateau. Seismograms recorded from the moment magnitude（MW） 5.4 Minxian earthquake enable obtaining an average crustal velocity model for this region. We initially carried out a series of FWA robustness tests in regional waveform inversion at the same earthquake and station positions across the study region,inverting two velocity structure models, with and without a low-velocity crustal layer; the accuracy of our average inversion results and their standard deviations reveal the advantages of the FWA for the inversion of regional seismic waveforms. We applied the FWA across our study area using three component waveform data recorded by nine broadband permanent seismic stations with epicentral distances ranging between 146 and 437 km. These inversion results show that the average thickness of the crust in this region is 46.75 km, while thicknesses of the sedimentary layer, and the upper, middle, and lower crust are 3.15,15.69, 13.08, and 14.83 km, respectively. Results also show that the P-wave velocities of these layers and the upper mantle are 4.47, 6.07, 6.12, 6.87, and 8.18 km/s,respectively.
基金funded by the National Science & Technology Pillar Program in the 12th "Five-year Plan" Period,China(2012BAKI9B02)
文摘An algorithm for detecting low-frequency seismic events is developed and applied to the detection of low-frequency events before the 2008 Wenchuan and the 2013 Lushan earthquakes. Continuous vertical-component waveforms of some broadband stations in the few months before the Wenchuan and Lushan earthquakes are processed by applying a bandpass filter in 2- 8Hz,and then converted to envelopes with a smoothing time of 10 s window and a median filter with a 20 min window. As a result,teleseismic,long-period noise and local small earthquakes are removed,the filtered amplitude is obviously larger than that of the noise and lasts for a dozen minutes to several hours during a few days in a few stations before the Wenchuan and Lushan earthquakes,respectively. The waveform and envelope are similar to that of a non-volcanic tremor( NVT). There are suspected NVT before the two earthquakes. Preliminary application demonstrates that this algorithm is potentially useful for extracting NVT signals from continuous seismic waveforms.
文摘Taking the fluvial reservoir of the Neogene Minghuazhen Formation in Bozhong S oilfield in China as an example, a detailed study of the interlayer in the reservoir was conducted. From the perspective of sedimentary genesis of the interlayer, three types of genesis of the interlayer are summarized and analyzed, namely, fine grain sediment in the inter peak channel, suspended sediment in the post flood channel, and abandoned channel sediment. At the same time, combined with seismic waveform analysis, the distribution characteristics and morphology of the interlayer in complex fluvial facies oilfield are carefully depicted, and the horizontal well optimization implementation is guided based on the planar and three-dimensional spatial distribution characteristics of the interlayer. This method enriches the characterization technology of interlayer in offshore oilfields, and has important guiding significance for the overall evaluation and development research of complex fluvial facies oilfields.
基金supported by Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(No.2020CX010202).
文摘The Jurassic Lianggaoshan Formation in eastern Sichuan Basin is a key target for shale oil exploration.It faces challenges in three-pressure prediction due to complex structural and sedimentary interactions,as well as strong reservoir anisotropy.These issues often lead to wellbore instability and gas logging anomalies during drilling.This study presents an integrated workflow that combines residual moveout correction using correlation-based dynamic time warping(CDTW),high-resolution seismic waveform indication inversion,and three-pressure prediction of jointing well-seismic data.Applied to the LT1 well block,the workflow effectively corrects anisotropic residual moveout in image gathers,leading to a signal strength increase of over 10%in frequency bands above 30 Hz and enhancing event continuity.High-resolution rock mechanical parameters are obtained through seismic waveform inversion and regional calibration,enabling the prediction of three-dimensional pore pressure,collapse pressure and fracture pressure.The results are consistent with actual drilling gas shows and core data,confirming the method's accuracy and supporting mud weight planning and wellbore stability efforts.This cost-effective and technically robust approach proves highly reliable in complex environments with significant heterogeneity and anisotropy,assisting drilling decisions and risk management in eastern Sichuan and similar challenging geological settings.
文摘The Support Vector Machine （SVM） method can be used to set up a nonlinear function prediction model. It is based on the small sample learning theory. The kernel function can be constructed automatically based on the actual sample data by using the SVM method. As a result, the function not only gets a higher fit precision but is also better generalized. The frequency spectrum and seismic waveform are related by Fourier transform, so they are two different forms of the same physical phenomenon. The variety of waveform character reflects stratigraphic differences and frequency spectrum differences reflect the variation of lithology, fluid composition, and formation thickness. It directly predicts sandstone thickness using the seismic waveform. This not only fully utilizes the seismic information but also greatly increases the accuracy of the prediction. Model examples and actual applications show the applicability of this method.
基金the National Natural Science Foundation of China(Grant Nos.42030311,and 42325401)the Science and Tech-nology Innovation Talent Program of Hubei Province(Grant No.2022EJD015).
文摘The Mw 6.8 Adassil earthquake that occurred in the High Atlas on September 8,2023,was a catastrophic event that provided a rare opportunity to study the mechanics of deep crustal seismicity.This research aimed to decipher the rupture characteristics of the Adassil earthquake by analyzing teleseismic waveform data in conjunction with interferometric synthetic aperture radar(InSAR)observations from both ascending and descending orbits.Our analysis revealed a reverse fault mechanism with a centroid depth of approximately 28 km,exceeding the typical range for crustal earthquakes.This result suggests the presence of cooler temperatures in the lower crust,which facilitates the accumulation of tectonic stress.The earthquake exhibited a steep reverse mechanism,dipping at 70°,accompanied by minor strike-slip motion.Within the geotectonic framework of the High Atlas,known for its volcanic legacy and resulting thermal irregularities,we investigated the potential contributions of these factors to the initiation of the Adassil earthquake.Deep seismicity within the lower crust,away from plate boundaries,calls for extensive research to elucidate its implications for regional seismic hazard assessment.Our findings highlight the critical importance of studying and preparing for significant seismic events in similar geological settings,which would provide valuable insights into regional seismic hazard assessments and geodynamic paradigms.
基金supported by the National Natural Science Foundation of China (Grant Nos. 42030311, 41874068, 41974009)。
文摘Although the Sichuan basin is a stable block with low historical seismicity,the Suining M5.0 earthquake on January31,2010 occurred near the center of the basin,causing casualty and substantial damage.Previous studies have shown that the earthquake is very shallow and may occur in the sedimentary cover rocks,but its causative fault has not been identified.Based on local broadband seismic waveform data as well as a pair of ALOS PALSAR ascending orbit data,we explore the seismogenic mechanism via further constraining the source depth and the ruptured fault.The earthquake caused ground uplift in the southeast of the epicenter area,with a maximum line of sight displacement of about 13.6 cm,much larger than the displacement caused by a M5 earthquake at a typical depth of 10 km,which indicates that the earthquake is very shallow.Through joint inversion of seismic waveform and InSAR data,we obtain the moment magnitude of Suining earthquake as MW4.5,with the strike,dip,and rake of its fault plane as 17°,66° and 90°,respectively,and the centroid depth less than 1 km,supporting that the earthquake occurred at the shallow part of a high angle thrust fault dipping to the southeast.It is further confirmed that the earthquake may be triggered by the diffusion of high-pressure fluid migrating from the underside gas reservoir.
