The Longmenshan(LMS) fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards. Although regional ve...The Longmenshan(LMS) fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards. Although regional velocity models are available for the LMS fault zone, high-resolution velocity models are lacking. Therefore, a dense array of 240 short-period seismometers was deployed around the central segment of the LMS fault zone for approximately 30 days to monitor earthquakes and characterize fine structures of the fault zone. Considering the large quantity of observed seismic data, the data processing workflow consisted of deep learning-based automatic earthquake detection, phase arrival picking, and association. Compared with the earthquake catalog released by the China Earthquake Administration, many more earthquakes were detected by the dense array. Double-difference seismic tomography was adopted to determine V_(p), V_(s), and V_(p)/V_(s) models as well as earthquake locations. The checkerboard test showed that the velocity models have spatial resolutions of approximately 5 km in the horizontal directions and 2 km at depth. To the west of the Yingxiu–Beichuan Fault(YBF), the Precambrian Pengguan complex, where most of earthquakes occurred, is characterized by high velocity and low V_(p)/V_(s) values. In comparison, to the east of the YBF, the Upper Paleozoic to Jurassic sediments, where few earthquakes occurred, show low velocity and high V_(p)/V_(s) values. Our results suggest that the earthquake activity in the LMS fault zone is controlled by the strength of the rock compositions. When the high-resolution velocity models were combined with the relocated earthquakes, we were also able to delineate the fault geometry for different faults in the LMS fault zone.展开更多
At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and ...At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following： （1） The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. （2） Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. （3） The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5-20 km. （4） The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152~, 74~ and 8~, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 kin. The co-seismic rupture mainly concentrates at depths of 3-13 km, with a moment magnitude （Mw） of 6.5. （5） The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations： dip angle varies within 660-89~ from northwest to southeast and the average dip angle measures -84~. The results of this work are of fundamental importance for further studies on the source characteristics, tectonic environment, and seismic hazard evaluation of the Jiuzhaigou earthquake.展开更多
A unique characteristic of piezoelectric materials is their ability of electric-mechanical transduction and converting mechanical energy to electrical energy or vice versa. This remarkable property, embedded in piezoe...A unique characteristic of piezoelectric materials is their ability of electric-mechanical transduction and converting mechanical energy to electrical energy or vice versa. This remarkable property, embedded in piezoelectric materials, has been exploited to construct a wide variety of acoustic transducers for industrial applications. These include acoustic experimental measurements [1-3], mobile and internet communications [4,5], intravascular ultrasound [6], medical imaging [7], rangefinders [8], fingerprint sensors, implantable micro-devices, nondestructive detection, mea-surement of the in-situ stresses of underground rock formation, and early warning systems for dam damage and natural hazards, among others.展开更多
基金supported by the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology under Grant 2024yjrc64the National Key R&D Program of China under Grant 2018YFC1504102。
文摘The Longmenshan(LMS) fault zone is located at the junction of the eastern Tibetan Plateau and the Sichuan Basin and is of great significance for studying regional tectonics and earthquake hazards. Although regional velocity models are available for the LMS fault zone, high-resolution velocity models are lacking. Therefore, a dense array of 240 short-period seismometers was deployed around the central segment of the LMS fault zone for approximately 30 days to monitor earthquakes and characterize fine structures of the fault zone. Considering the large quantity of observed seismic data, the data processing workflow consisted of deep learning-based automatic earthquake detection, phase arrival picking, and association. Compared with the earthquake catalog released by the China Earthquake Administration, many more earthquakes were detected by the dense array. Double-difference seismic tomography was adopted to determine V_(p), V_(s), and V_(p)/V_(s) models as well as earthquake locations. The checkerboard test showed that the velocity models have spatial resolutions of approximately 5 km in the horizontal directions and 2 km at depth. To the west of the Yingxiu–Beichuan Fault(YBF), the Precambrian Pengguan complex, where most of earthquakes occurred, is characterized by high velocity and low V_(p)/V_(s) values. In comparison, to the east of the YBF, the Upper Paleozoic to Jurassic sediments, where few earthquakes occurred, show low velocity and high V_(p)/V_(s) values. Our results suggest that the earthquake activity in the LMS fault zone is controlled by the strength of the rock compositions. When the high-resolution velocity models were combined with the relocated earthquakes, we were also able to delineate the fault geometry for different faults in the LMS fault zone.
基金funded by the Seismological Bureau Spark Program Project(Grant No.XH15007)the National Natural Science Foundation of China(Grant Nos.41604058,41574057,41621091)the Sichuan-Yunnan National Seismological Monitoring and Prediction Experimental Station Project(Grant No.2016CESE0204)
文摘At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following： （1） The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. （2） Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. （3） The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5-20 km. （4） The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152~, 74~ and 8~, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 kin. The co-seismic rupture mainly concentrates at depths of 3-13 km, with a moment magnitude （Mw） of 6.5. （5） The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations： dip angle varies within 660-89~ from northwest to southeast and the average dip angle measures -84~. The results of this work are of fundamental importance for further studies on the source characteristics, tectonic environment, and seismic hazard evaluation of the Jiuzhaigou earthquake.
基金supported by Xi’an University of Posts and Telecommunicationsthe Physical Sciences Division at The University of Chicago
文摘A unique characteristic of piezoelectric materials is their ability of electric-mechanical transduction and converting mechanical energy to electrical energy or vice versa. This remarkable property, embedded in piezoelectric materials, has been exploited to construct a wide variety of acoustic transducers for industrial applications. These include acoustic experimental measurements [1-3], mobile and internet communications [4,5], intravascular ultrasound [6], medical imaging [7], rangefinders [8], fingerprint sensors, implantable micro-devices, nondestructive detection, mea-surement of the in-situ stresses of underground rock formation, and early warning systems for dam damage and natural hazards, among others.
