利用GDSN宽频带资料研究青海地区1988～1990年强震的震源过程

STUDIES ON SOURCE PROCESSES OF SEVERAL STRONG EARTHQUAKES IN QINGHAI REGION FROM 1988 TO 1990 FROM GDSN BROADBAND DATA

1988至1990年，青海地区发生了4次震级大于6．0的强震。利用GDSN宽频带波形资料，通过波形模拟，结合地质构造的背景资料对这几次地震进行了震源破裂和发震构造背景的研究。使用台站的准震源时间函数（qSTE）和准时间差（qTD）的分析方法，对震源的复杂性进行了讨论。1988年11月5日沱沱河沿Ms6．3地震是一个由两次子破裂组成的复杂震源过程的地震；1990年1月14日茫崖Ms6．1地震发生于重力异常带的交汇处，破裂扩展方面与断层走向一致；1990年4月26日共和Ms6．9与mb6．3地震的震源过程更为复杂，Ms6．9地震由两次子破裂组成，约30s后发生的mb6．3地震是一个独立于Ms6．9地震的大破裂。本文的研究从震源分析的角度进一步支持了青藏高原东北部构造应力的压力轴为接近水平的NE向，随着向青藏高原北部的推移，其构造应力的压力轴逆时针转为接近水平的NEE或N－S向的结论。

From 1888 to 1990, four strong earthquakes which magnitudes were larger than 6.0 ocurred in Qinghai province. Using the GDSN broadband waveform data, both the seismic source rupture features and seismogenic tectonic background of these eaxthquakes are studied combining with geologic data by waveform modelling. Specially, a method of station quasi - source time function (qSTE) and quasi - the difference (qTD) is used to dicuss the complexity of source process. The Ms6.3 Totoheyan earthquake on 5th November 1988 is an event of complicated source process composed of two subevents. The Ms6.1 Mangya earthquake on 14th January 1990 is locted at a convergence of gravity anomaly zones, which rupture propagation direction corresponds with fault direction. It is more complicated for two Ms6.9 and Ms6.3 Gonghe earthquakes on 26th April 1990, in which the former is composed of two subevents and the latter, which occurred for about 30 seconds late than the former, is a large independent repture.According to the source analysis, it is further suggested to the conclusion that the pressure axies of the tectonic stress field in the northeast of Qinghai-Xizang plateau is oriental to NE-SW close to horizontal direction, and with the evolvemen toward the north of Qinghai-Xizang plateau it is changed anticlockwisely to NEE - SSW or N - S close to horizontal direction.