With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full wavefo...With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of ii kin, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11 16 kin, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an Ms6.1 earthquake.展开更多
In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequ...In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequestration while enhancing hydrocarbon recovery.However,variations in injection parameters at the wellhead can exert pronounced effects on the temperature and pressure conditions at the bottomof the well.These variations,in turn,influence the geomechanical behavior of reservoir rocks and the displacement efficiency of CO_(2) within the formation.Precise prediction of downhole thermodynamic conditions is therefore essential for optimizing injection performance and ensuring reservoir stability.To address this need,the present study develops a robust coupled model to simulate the behavior of CO_(2) within the wellbore,incorporating momentum conservation,mass continuity,and steady-state heat transfer equations.Validation against field-measured data confirms the model’s reliability and applicability under realworld operating conditions.Parametric analysis reveals the complex influence of injection conditions on bottom-hole states.Injection pressure primarily affects downhole pressure,exerting minimal influence on temperature.In contrast,low injection temperatures and elevated flow rates lead to reduced bottom-hole temperatures and heightened pressures.Owing to the interplay of convective and conductive heat transfer mechanisms,the relationship between injection rate and bottom-hole temperature exhibits nonlinearity.Notably,injection scenarios characterized by low temperature,high pressure,and high velocity promote a deeper penetration of the CO_(2) critical phase transition point within the tubing.Among the parameters examined,injection temperature emerges as the dominant factor affecting the depth of CO_(2)’s phase transformation,followed by injection rate,with pressure exerting the least influence.A strong correlation is observed between injection rate and the depth of the critical phase transition,offering a practical framework for tailoring injection strategies to enhance both CO_(2) storage capacity and recovery efficiency.展开更多
The dense broadband seismic network provides more high-quality waveform that is helpful to improve constraint focal depth of shallow earthquake. Many shal- low earthquakes occurring in sediment were regarded as induce...The dense broadband seismic network provides more high-quality waveform that is helpful to improve constraint focal depth of shallow earthquake. Many shal- low earthquakes occurring in sediment were regarded as induced events. In Sichuan basin, gas industry and salt mining are dependent on fluid injection technique that triggers microseismicity. We method with regional records adopted waveform inversion to obtain focal mechanism of an Ms4.8 earthquake at Changning. The result suggested that the Changning earthquake occurred at a ESE thrust fault, and its focal depth was about 3 km. The depth phases including teleseismic pP phase and regional sPL phase shows that the focal depth is about 2 km. The strong, short- period surface wave suggests that this event is a very shallow earthquake. The amplitude ratio between Rayleigh wave and direct S wave was also used to estimate the source depth of the mainshock. The focal depth （2-4 km） is far less than the depth of the sedimentary layer thickness （6-8 km） in epicentral region. It is close to the depth of fluid injection of salt mining, which may imply that this event was triggered by the industrial activity.展开更多
Three-dimensional P-and S-wave velocities（vP,vS）,Poisson＇s ratio（σ）,crack-density（ε） and bulk-sound velocity（vφ） structures along the slab upper boundary beneath the fore-arc regions were determined using ...Three-dimensional P-and S-wave velocities（vP,vS）,Poisson＇s ratio（σ）,crack-density（ε） and bulk-sound velocity（vφ） structures along the slab upper boundary beneath the fore-arc regions were determined using a large number of high-quality P-wave and S-wave arrival times from both onshore and offshore earthquakes in Japan.The velocity and Poisson＇s ratio images provide a compelling evidence for a highly hydrated and serpentinized fore-arc mantle and fluid-bearing anomalous low velocity and high Poisson＇s ratio associated with slab dehydration under the fore-arc areas.Most great thrust earthquakes（M〉7.5） occurred at or close to the high-velocity areas along the slab interface under the fore-arc areas,suggesting strong interplate coupling（asperities） with slab subduction.On the other hand,prominent low-velocity anomalies were revealed along the slab upper boundary,which may reflect weak coupled or decoupled patches（aseismicity） of the plates due to serpentinization of the fore-arc mantle wedge.The crack-density and bulk-sound velocity images,calculated from the corresponding velocity models,indicate that the interplate coupling in northeastern Japan is different from that under central and southwestern Japan owing to differences between the tectonic backgrounds of the subduction system,such as the geological age,thermal regime and dipping angle of the oceanic plates.A comparison between fluid-related anomalies of Japan,Cascadia,Chile,and Costa Rica subduction zones suggests that seismic mantle may be common in fore-arc settings and these reflect similar 3-D seismic structures relatively to fluid liberating processes.We consider that the fluid-bearing anomalies along the interface of the subducting slab,attributing to processes such as slab dehydration and serpentinization of the fore-arc mantle,are mainly contributed to the interplate coupling and the repeated generation of the great thrust earthquakes under the fore-arc regions in Japan.展开更多
Focal depths of the 2008 Ms6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated.Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M≥3.0 were ...Focal depths of the 2008 Ms6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated.Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M≥3.0 were determined using the seismic depth phase sPL;additionally,the focal depths of 232 earthquakes were measured by fitting the threecomponent waveforms of the P and S waves.The source depth of the main shock is^12 km.The majority of the aftershocks with magnitude M≥3.0 occurred in the brittle upper crust at the depths range of 12-18 km.Further,the Source mechanisms of the 232events around the Panzhihua earthquake source area were determined,and the results show that the earthquakes have predominantly strike-slip mechanisms in the Dianzhong Block,but display complexity of the focal mechanisms outside and near the boundary of the Dianzhong block.The 232 earthquake mechanisms from this study are combined with the solutions from the Global Centroid Moment Tensor (GCMT) catalog to derive 2D stress field.The inversion results show that the Dianzhong block is predominantly under a strike slip faulting regime and the direction of the maximum principal compressionσ1 is northwestsoutheast (NW-SE)-trending.The distribution is coincide with GPS velocity field.However,orientations of principal stress axes as well as the faulting types change outside and near the Dianzhong block.The results show that the tectonic stress field in the study area is predominantly controlled by the southeast (SE)-trending horizontal movement and clockwise rotation of the Dianzhong block as a result of the eastward movement of eastern Tibetan meeting the old and rigid South China block (SCB).The Panzhihua earthquake ruptured at^12 km depth where the tectonic stress regime is under the SE-direction horizontal compression and the NE-direction horizontal extension.展开更多
基金financial supported by Joint Seismological Science Foundation of China (No.200808078)National Natural Science Foundation of China (Nos.40821160549 and 41074032)
文摘With the 2008 Ms6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches： （1） using the depth phase sPL and （2） using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of ii kin, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11 16 kin, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an Ms6.1 earthquake.
基金supported by the National Natural Science Foundation of China(Nos.52304046,52204051,52174033 and U23B20156).
文摘In the context of the global“Carbon Peaking and Carbon Neutrality”initiative,the injection of carbon dioxide(CO_(2))into depleted gas reservoirs represents a dual-purpose strategy—facilitating long-term carbon sequestration while enhancing hydrocarbon recovery.However,variations in injection parameters at the wellhead can exert pronounced effects on the temperature and pressure conditions at the bottomof the well.These variations,in turn,influence the geomechanical behavior of reservoir rocks and the displacement efficiency of CO_(2) within the formation.Precise prediction of downhole thermodynamic conditions is therefore essential for optimizing injection performance and ensuring reservoir stability.To address this need,the present study develops a robust coupled model to simulate the behavior of CO_(2) within the wellbore,incorporating momentum conservation,mass continuity,and steady-state heat transfer equations.Validation against field-measured data confirms the model’s reliability and applicability under realworld operating conditions.Parametric analysis reveals the complex influence of injection conditions on bottom-hole states.Injection pressure primarily affects downhole pressure,exerting minimal influence on temperature.In contrast,low injection temperatures and elevated flow rates lead to reduced bottom-hole temperatures and heightened pressures.Owing to the interplay of convective and conductive heat transfer mechanisms,the relationship between injection rate and bottom-hole temperature exhibits nonlinearity.Notably,injection scenarios characterized by low temperature,high pressure,and high velocity promote a deeper penetration of the CO_(2) critical phase transition point within the tubing.Among the parameters examined,injection temperature emerges as the dominant factor affecting the depth of CO_(2)’s phase transformation,followed by injection rate,with pressure exerting the least influence.A strong correlation is observed between injection rate and the depth of the critical phase transition,offering a practical framework for tailoring injection strategies to enhance both CO_(2) storage capacity and recovery efficiency.
基金supported by China National Special Fund for Earthquake Scientific Research in Public Interest (201308013)China Postdoctoral Science Foundation (No. 2012M520431)the National Natural Science Foundation of China Grant No. 41204044
文摘The dense broadband seismic network provides more high-quality waveform that is helpful to improve constraint focal depth of shallow earthquake. Many shal- low earthquakes occurring in sediment were regarded as induced events. In Sichuan basin, gas industry and salt mining are dependent on fluid injection technique that triggers microseismicity. We method with regional records adopted waveform inversion to obtain focal mechanism of an Ms4.8 earthquake at Changning. The result suggested that the Changning earthquake occurred at a ESE thrust fault, and its focal depth was about 3 km. The depth phases including teleseismic pP phase and regional sPL phase shows that the focal depth is about 2 km. The strong, short- period surface wave suggests that this event is a very shallow earthquake. The amplitude ratio between Rayleigh wave and direct S wave was also used to estimate the source depth of the mainshock. The focal depth （2-4 km） is far less than the depth of the sedimentary layer thickness （6-8 km） in epicentral region. It is close to the depth of fluid injection of salt mining, which may imply that this event was triggered by the industrial activity.
基金supported by the research grants of the National Natural Science Foundation of China(Nos.40872148 and 40974024)the New Century Excellent Talents in University,Ministry of Education(NCET2009)
文摘Three-dimensional P-and S-wave velocities（vP,vS）,Poisson＇s ratio（σ）,crack-density（ε） and bulk-sound velocity（vφ） structures along the slab upper boundary beneath the fore-arc regions were determined using a large number of high-quality P-wave and S-wave arrival times from both onshore and offshore earthquakes in Japan.The velocity and Poisson＇s ratio images provide a compelling evidence for a highly hydrated and serpentinized fore-arc mantle and fluid-bearing anomalous low velocity and high Poisson＇s ratio associated with slab dehydration under the fore-arc areas.Most great thrust earthquakes（M〉7.5） occurred at or close to the high-velocity areas along the slab interface under the fore-arc areas,suggesting strong interplate coupling（asperities） with slab subduction.On the other hand,prominent low-velocity anomalies were revealed along the slab upper boundary,which may reflect weak coupled or decoupled patches（aseismicity） of the plates due to serpentinization of the fore-arc mantle wedge.The crack-density and bulk-sound velocity images,calculated from the corresponding velocity models,indicate that the interplate coupling in northeastern Japan is different from that under central and southwestern Japan owing to differences between the tectonic backgrounds of the subduction system,such as the geological age,thermal regime and dipping angle of the oceanic plates.A comparison between fluid-related anomalies of Japan,Cascadia,Chile,and Costa Rica subduction zones suggests that seismic mantle may be common in fore-arc settings and these reflect similar 3-D seismic structures relatively to fluid liberating processes.We consider that the fluid-bearing anomalies along the interface of the subducting slab,attributing to processes such as slab dehydration and serpentinization of the fore-arc mantle,are mainly contributed to the interplate coupling and the repeated generation of the great thrust earthquakes under the fore-arc regions in Japan.
基金supported by the National Natural Science Foundation of China (Grant No. 41974063)the Basic Research Fund of the Institute of Earthquake Forecasting, China Earthquake Administration (Grant No. 2015IES010302)the State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences (Grant No. SKLGED2018-4-3-E)
文摘Focal depths of the 2008 Ms6.1 Panzhihua earthquake sequence and tectonic stress field in the source area are investigated.Source depths of 24 earthquakes in Panzhihua earthquake sequence with a magnitude M≥3.0 were determined using the seismic depth phase sPL;additionally,the focal depths of 232 earthquakes were measured by fitting the threecomponent waveforms of the P and S waves.The source depth of the main shock is^12 km.The majority of the aftershocks with magnitude M≥3.0 occurred in the brittle upper crust at the depths range of 12-18 km.Further,the Source mechanisms of the 232events around the Panzhihua earthquake source area were determined,and the results show that the earthquakes have predominantly strike-slip mechanisms in the Dianzhong Block,but display complexity of the focal mechanisms outside and near the boundary of the Dianzhong block.The 232 earthquake mechanisms from this study are combined with the solutions from the Global Centroid Moment Tensor (GCMT) catalog to derive 2D stress field.The inversion results show that the Dianzhong block is predominantly under a strike slip faulting regime and the direction of the maximum principal compressionσ1 is northwestsoutheast (NW-SE)-trending.The distribution is coincide with GPS velocity field.However,orientations of principal stress axes as well as the faulting types change outside and near the Dianzhong block.The results show that the tectonic stress field in the study area is predominantly controlled by the southeast (SE)-trending horizontal movement and clockwise rotation of the Dianzhong block as a result of the eastward movement of eastern Tibetan meeting the old and rigid South China block (SCB).The Panzhihua earthquake ruptured at^12 km depth where the tectonic stress regime is under the SE-direction horizontal compression and the NE-direction horizontal extension.
