In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred...In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the Chuandian rhombic block have strike-slip mechanism. The orientations of maximum compressive stresses obtained from source mechanism are changed from NNW-SSN to NS in the areas from north to south of the block, and tensile stresses are mainly in ENE-WSW or NE-SE. In the eastern Tibetan Plateau, the orientations of maximum compressive stress radiate toward outside from the plateau, and the tensile stress orientations mostly parallel to arc structures. Near 28N the orientations of both maximum compressive stress and tensile stress changed greatly, and the boundary seems to correspond to the southwestern extended line of Longmenshan fault. Outside of the Chuandian rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-moderate events presented in the paper is consistence with that of moderate-strong earthquakes determined by Harvard University, which means the source mechanism of small-moderate events can be used to study the tectonic stress field in this region.展开更多
Seism is one of the main triggering mechanisms of forming fluxoturbidite in front of delta. The forming process of fluxoturbidite in front of delta under seismism was experimentally simulated in lab. The results show ...Seism is one of the main triggering mechanisms of forming fluxoturbidite in front of delta. The forming process of fluxoturbidite in front of delta under seismism was experimentally simulated in lab. The results show that there are two kinds of slumping and three kinds of fluxoturbidites in front of delta under seismism. The liquefied fluxo- turbidite and secondary overlapped turbidite move by their own gravity, and develop mainly on the base of foreslope and the frontal bed slope. They have a small sedimentary scale and can’t move too far. On the contrary, the faulted fluxoturbidites have a larger scale and can move a long distance. The collision- power from hinder overlapped sand body is also the motivity of the faulted fluxoturbidite’s migration besides its own gravity. They mostly develop in the deep sag in front of delta, and are the favorable room to accumulate petroleum. Finally, according to the demonstration and inversion of similarity, at least 7.35 M of earthquake had happened in middle- Shasan period of Paleogene, which induced the slumping of delta front. So the tectonic action of northern steep slope is the main reason to induce earth- quake.展开更多
Donald V.Helmberger was an unparalleled observational seismologist,and theoretician.His pioneering work in seismic waveform modeling,and the numerical methods he developed to simulate seismograms to study the structur...Donald V.Helmberger was an unparalleled observational seismologist,and theoretician.His pioneering work in seismic waveform modeling,and the numerical methods he developed to simulate seismograms to study the structure of the Earth and the nature of earthquake sources have become techniques that are now commonplace.展开更多
基金The National Key Basic Research Program under the Project "Mechanism and Prediction of Continental Strong Earthquake"(G1998040700) and Joint Seismological Science Foundation of China (100108).
文摘In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the Chuandian rhombic block have strike-slip mechanism. The orientations of maximum compressive stresses obtained from source mechanism are changed from NNW-SSN to NS in the areas from north to south of the block, and tensile stresses are mainly in ENE-WSW or NE-SE. In the eastern Tibetan Plateau, the orientations of maximum compressive stress radiate toward outside from the plateau, and the tensile stress orientations mostly parallel to arc structures. Near 28N the orientations of both maximum compressive stress and tensile stress changed greatly, and the boundary seems to correspond to the southwestern extended line of Longmenshan fault. Outside of the Chuandian rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-moderate events presented in the paper is consistence with that of moderate-strong earthquakes determined by Harvard University, which means the source mechanism of small-moderate events can be used to study the tectonic stress field in this region.
基金Project 2001BA605A09 supported by national key project of the tenth Five- Year Plan
文摘Seism is one of the main triggering mechanisms of forming fluxoturbidite in front of delta. The forming process of fluxoturbidite in front of delta under seismism was experimentally simulated in lab. The results show that there are two kinds of slumping and three kinds of fluxoturbidites in front of delta under seismism. The liquefied fluxo- turbidite and secondary overlapped turbidite move by their own gravity, and develop mainly on the base of foreslope and the frontal bed slope. They have a small sedimentary scale and can’t move too far. On the contrary, the faulted fluxoturbidites have a larger scale and can move a long distance. The collision- power from hinder overlapped sand body is also the motivity of the faulted fluxoturbidite’s migration besides its own gravity. They mostly develop in the deep sag in front of delta, and are the favorable room to accumulate petroleum. Finally, according to the demonstration and inversion of similarity, at least 7.35 M of earthquake had happened in middle- Shasan period of Paleogene, which induced the slumping of delta front. So the tectonic action of northern steep slope is the main reason to induce earth- quake.
文摘Donald V.Helmberger was an unparalleled observational seismologist,and theoretician.His pioneering work in seismic waveform modeling,and the numerical methods he developed to simulate seismograms to study the structure of the Earth and the nature of earthquake sources have become techniques that are now commonplace.
