科里奥利力效应与昆仑山口西8.1级地震后两侧地震活动的可能关系

根据物理学中科里奥利力原理,分析了以走滑断层为主的大地震产生的科里奥利力对地震断层两侧邻近地区地震活动的可能影响。结果表明,在昆仑山口西8.1级地震后东昆仑断裂带南北两侧邻近地区较大地震一般发生在8.1级地震产生的科里奥利力引起的库仑破裂应力增加地区。

A Discussion of Some Problems Concerning the Tosonhu Lake M_S7.5 Earthquake in 1937

The East Kuulun active fault zone, which lies in the valley of the Kuulun Mountains above an elevation of 4,000 meters, is an important active fault zone in the Northeast Qinghai-Xizang （Tibet） Plateau. The 1937, the Tosonhu lake Ms7. 5 earthquake occurred in the eastern segment of the East Kuulun active fault zone. Four field investigations were launched on this seism in 1963, 1971, 1980, and between 1986 and 1990. However, due to different extents of the investigations, four different conclusions have been gained. Concerning the length aspect of the surface rupture zone of this earthquake, the unanimous consensus is that its eastern end lies in the west side of the main Ridge of the A ＇nyemaqen Mountains, but opinions about the western end and the location of the macro-epicenter are different. Based on investigation and comprehensive study, a series of scientific problems like geometric and kinetic characteristics, the length of the rupture zone, the maximum sinistral horizontal displacement and the macroepicenter were re-evaluated. We believe that the total length of this earthquake＇s surface deformation zone is at least 240km; the western end of the zone is at the west of Wnsuwuwoguole; the maximum sinistral horizontal displacement is 8m to the west of Baerhalasha gully on the east side of Sanchakou; the maximum vertical displacement is 3.5m in the south of Sanchakou and the macro-epicenter is in Sanchakou.

Earthquake Surface Rupture Features and Tectonic Significance of the Tazang Fault in the Eastern Part of the East Kunlun Fault Zone

The East Kunlun fault zone is located in the northern margin of the Bayan Har block. The study of earthquake rupture behavior in the fault zone is of importance for understanding the future seismic risk in northwest Sichuan. A number of geological field investigations, typical micro topography DGPS measurements and sample dating show that the earthquake activity of the East Kunlun fault zone extends to the north boundary of Zoige basin, a segment known as the Luocha segment of Tazang fault. In the satellite image, the segment is seen clearly as gray and yellow strips. The earthquake deformation zone mainly features fault scarp, valleys on the slope, offset gullies and terraces, linear distribution of plants, waterfall, fault spring, fault sag pond, and landslide, collapse and talus associated with surface rupturing. These phenomena are distributed intermittently along the re-existing fault and form a ～50km-long inverse L-shaped deformation zone. Fault activities caused left-lateral offset of gullies and terraces, with horizontal displacement concentrated at 5.5m^6m, 18m～23m, 68m～75m, and 200m～220m, respectively. The recent earthquake occurred between 340±30～500±30BP. The macro epicenter is located 5km～7km northwest of Benduo village, with magnitude of MW7.3～7.4, maximum coseismic displacement of 6m, horizontal displacement 5.5m～6m and vertical displacement 0.2m～0.5m, being in a proportion of 5∶1～10∶1. These phenomena show that the Tazang fault is the causative fault of this earthquake. The fault is a Holocene active fault and was dominated recently by left-lateral movement with a small amount of thrust component under compressive shear stress. This characteristic is similar to the movement in other segments of the East Kunlun fault zone. The results of this study support the "continental escape" model.

A Preliminary Study of Palaeo-earthquakes on the Maqu Fault of East Kunlun Fault Zone

The East Kunlun active fault is an important NWW-trending boundary fault on the northeastern margin of the Qinghai-Xizang (Tibet) Plateau. The Maqu fault is the easternmost segment of the East Kunlun active fault. Based on three trenches, four Holocene palaeo-earthquake events are identified along the Maqu fault. The latest palaeo-earthquake event is (1730±50) ～ (1802±52) a BP, the second is (3736±57) ～ (4641±60) a BP, the third is (8590±70) a BP, and the earliest is (12200±1700) ka BP. The time of the first and second palaeo-earthquake events is more reliable than that of the third and last ones. As a result, the recurrence interval of the palaeo-earthquakes on the easternmost segment of the East Kunlun active fault is approximately 2400 a, and the palaeo-earthquake elapsed time is (1730±50) ～ (1802±52) a BP.

Microseismic Concentration Zones before and after the February 12,2014 M_S 7.3 Yutian Earthquake and the Possible Indication of an Earthquake Risk Zone

Since 2001, there have occurred in succession the 2001 Kunlun Mountains M S8. 1earthquake,the 2008 Wenchuan M S8. 0 earthquake,the 2010 Yushu M S7. 1 earthquake and the 2012 Lushan M S7. 0 earthquake in the periphery of the Bayan Har block. By comparison of the characteristics of seismic strain release variations before and after the Kunlun Mountains M S8. 1 earthquake in the same time length in the geodynamical related regions,we found that the seismic strain release was obviously enhanced after the earthquake in the Longmenshan area,Batang area,and the NS-trending valleys at the west of the Hot Spring Basin. The Wenchuan earthquake occurred in the first area,and the Yushu earthquake is related to the second area. After the earthquake rupture occurred on the East Kunlun fault zone on the northern boundary of the Bayan Har Block,crustal materials on the south side of the fault zone migrated to the southeast,leading to a concentration of tectonic deformation in the Longmenshan thrust belt, e ventually rupturing on the Longmenshan thrust belt. This earthquake case illustrates that seismicity enhancement zones are possibly prone to long-term destructive earthquakes. After the M S7. 3 earthquake in Yutian,Xinjiang on February 12,2014,earthquake frequency and seismic strain release markedly increased in the junction area between the eastern Qilian Mountain tectonic belt and the Altun Tagh fault zone,where more attention should be paid to the long-term seismic risk.