The aftershock activity of the May 12, 2008 Wenchuan Ms8.0 Earthquake Sequence shows an obvious segmented feature. Most of the large aftershocks were distributed in the north and south parts of the aftershock zone. Th...The aftershock activity of the May 12, 2008 Wenchuan Ms8.0 Earthquake Sequence shows an obvious segmented feature. Most of the large aftershocks were distributed in the north and south parts of the aftershock zone. Thrusting was dominant with a small amount of strike-slip component in the south part. The aftershock activity decayed gradually, presenting the sequence features of a mainshock-aftershock pattern. The north part was the ending area of the malnshock fracture where strike-slipping was dominant, showing an obvious swarm feature. Therefore it became the major area for large aftershocks. The modulation of the earth tide on aftershock activity is remarkable; most large aftershocks occur during the period of flood and neap tide. The time period around 16：00 was the dominant occurring time for large aftershocks. The p-value, a parameter of modified Omori formula, increases gradually with time, and reaches about 1 at the end. Based on previous study, the sequence patterns, magnitude of maximum aftershock, as well as the duration of aftershock activity has been discussed. The primary results also show that the magnitude difference between the maiushock and the maximum aftershock is proportional to the rupture size of the maiushock for huge earthquakes of about Ms8.0. This means that when the magnitudes of the earthquakes are nearly the same, large rupture size corresponds to sufficient energy release.展开更多
Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of pol...Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.展开更多
The Tanlu （Tancheng-Lujiang） fault is one of the major structures in eastern China, which cuts across different blocks and controls the tectonic activity. Using the seismic data from the China Earthquake Networks Ce...The Tanlu （Tancheng-Lujiang） fault is one of the major structures in eastern China, which cuts across different blocks and controls the tectonic activity. Using the seismic data from the China Earthquake Networks Center, we investigate the spatial variations of the b-value in the Dabie-Sulu （Jiangsu-Shandong） organic belt by calculating the b-value of each grid （1~ xl~） from 1970 to 2010. The study shows that： the b-value is smaller in the Tanlu fault and its adjacent area, which might suggest that the major earthquake recurrence period is relatively long due to the lower frequency of small earthquake activity. In both sides of Tanlu fault, the b-value is higher at the edge of Sulu block and the eastern part of Dabie orogenic belt. The b values are higher in North China central orogenic belt, and small earthquake activity which occurred along the central orogenic belt is frequent. Additionally, combined with geological and geophysical study, we find that the b-value has a certain correspondence relationship with the lithologic distribution, which informs us that seismic activity features are closely related to the inhomogeneous media in the crust.展开更多
基金sponsored jointly by the Earthquake Scientific Research Program(200708020)the State Scientific and Technologic Support Programof the tenth"Five-Year Plan"(200704032006BAC01B030202)
文摘The aftershock activity of the May 12, 2008 Wenchuan Ms8.0 Earthquake Sequence shows an obvious segmented feature. Most of the large aftershocks were distributed in the north and south parts of the aftershock zone. Thrusting was dominant with a small amount of strike-slip component in the south part. The aftershock activity decayed gradually, presenting the sequence features of a mainshock-aftershock pattern. The north part was the ending area of the malnshock fracture where strike-slipping was dominant, showing an obvious swarm feature. Therefore it became the major area for large aftershocks. The modulation of the earth tide on aftershock activity is remarkable; most large aftershocks occur during the period of flood and neap tide. The time period around 16：00 was the dominant occurring time for large aftershocks. The p-value, a parameter of modified Omori formula, increases gradually with time, and reaches about 1 at the end. Based on previous study, the sequence patterns, magnitude of maximum aftershock, as well as the duration of aftershock activity has been discussed. The primary results also show that the magnitude difference between the maiushock and the maximum aftershock is proportional to the rupture size of the maiushock for huge earthquakes of about Ms8.0. This means that when the magnitudes of the earthquakes are nearly the same, large rupture size corresponds to sufficient energy release.
基金sponsored by the Natural Science of Shandong Province(ZH2014DQ019)Earthquake Science and Technology Spark Plan(XH15026)+1 种基金Key Foundation Program of Earthquake Administration of Shandong Province(JJ1407Y)the Contract Program of Earthquake Administration of Shandong Province(15Y102)
文摘Based on the seismic data of near-field source from the Shandong Digital Seismic Network,this study obtained the shear-wave splitting parameters from multiple stations. The results show that dominant directions of polarizations of fast shear-waves reflect the spatial distribution characteristics of tectonic stress in this area,CHD and LIS stations show 2 dominant directions,and reveals that the crustal seismic anisotropy in the Shandong area is constrained by the regional stress background,local failure and structure.
基金jointly supported by the Fundamental Research Funds for the Central Universities of China(ZY20140202)the Spark Program of Earthquake Science and Technology(XH15040Y)
文摘The Tanlu （Tancheng-Lujiang） fault is one of the major structures in eastern China, which cuts across different blocks and controls the tectonic activity. Using the seismic data from the China Earthquake Networks Center, we investigate the spatial variations of the b-value in the Dabie-Sulu （Jiangsu-Shandong） organic belt by calculating the b-value of each grid （1~ xl~） from 1970 to 2010. The study shows that： the b-value is smaller in the Tanlu fault and its adjacent area, which might suggest that the major earthquake recurrence period is relatively long due to the lower frequency of small earthquake activity. In both sides of Tanlu fault, the b-value is higher at the edge of Sulu block and the eastern part of Dabie orogenic belt. The b values are higher in North China central orogenic belt, and small earthquake activity which occurred along the central orogenic belt is frequent. Additionally, combined with geological and geophysical study, we find that the b-value has a certain correspondence relationship with the lithologic distribution, which informs us that seismic activity features are closely related to the inhomogeneous media in the crust.
