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一、引言青藏高原北东边界位于甘肃省、青海省和宁夏回族自治区三省的交界,是中国大陆现代构造运动最强烈的地区之一。这里还是青藏亚板块、南北地震构造带和华北亚板块相汇、重叠的构造部位,构造运动十分复杂。区内断层活动强度、位移速率和断裂规模位居我国活断裂之首。众多古地震和不断发生的现代大地震更说明这里正经历着强烈的现代构造运动。历史地震与现代地震的记载表明,地震总是和断层相并存,特别是7级以上的大地震,总伴有断层出现。因此,历史上曾有过断层引起地震还是地震产生断层的争论。1966年,Bracc和Byerlcc提出,已有断层上的粘滑运动可能是浅源地震的一种机制而被人们普遍接受,特别是像圣安德烈斯断层,地震确实是由断层突然运动造成的。
I. INTRODUCTION The northeast boundary of the Qinghai-Tibet Plateau lies at the junction of Gansu Province, Qinghai Province and the three provinces of Ningxia Hui Autonomous Region and is one of the strongest areas in modern Chinese tectonic movement in mainland China. Here is also the Qinghai-Tibet Plate, the North-South Seismic structural belt and the North China plate convergence, overlapping tectonic parts, tectonic movement is very complicated. The fault activity intensity, displacement rate and fault size in the area ranked the first in China. Many ancient earthquakes and the ongoing modern earthquakes further illustrate that there is a strong movement of modern tectonics here. Records of historical earthquakes and modern earthquakes show that earthquakes always coexist with faults, especially earthquakes of magnitude 7 and above, with the total occurrence of faults. Therefore, there has been a history of faults caused by earthquakes or earthquakes. In 1966 Bracc and Byerlcc suggested that the existing stick-slip movement on the fault may be a mechanism of shallow-earthquakes that are generally accepted, especially as the San Andreas Fault, which was caused by the sudden movement of the fault .