Abstract: Before the M_S 8.1 West Kunlun Mountain Pass earthquake,an orderly evolution of seismicity patterns was observed in the Qinghai-Tibet block:the evolution of seismic gaps showed a time span of several to decades of years and a space span of hundreds to thousands of kilometers,and that of seismic stripes had a time span of several years and a space span of thousands of kilometers.After 1990,the seismic precursory observation networks in Qinghai,Gansu,Sichuan,Xinjiang and Ningxia Provinces and autonomous regions recorded some typical far-field anomalies.These abnormal tendency changes roughly coincided with the formation time of seismogenic gaps and seismic stripes and were distributed in the Qilian Mountains tectonic zone,the East Kunlun tectonic belt,the West Qinling tectonic belt,the north-south tectonic belt and the Tianshan tectonic belt.The far-field anomalies and the spatial-temporal evolution of seismic gaps were complementary and correlated to each other.This article discusses the ordered and phased characteristics in the evolution of the above anomalies with the space-time preparation process of the M_S 8.1 earthquake.

Key words: the M_S 8.1 West Kunlun Mountain Pass earthquake, seismicity pattern, earthquake gap, far-field precursory anomaly

摘要： 昆仑山口西8.1级地震前,青藏块体出现了有序的地震图像演变过程:地震空区时间跨度数年至数十年,空间跨度数百至上千km;地震条带时间跨度数年,空间跨度数千km。1990年以后,青海、甘肃、四川、新疆、宁夏诸省的前兆观测台网记录到一批典型的远场前兆异常,这些趋势性异常变化与孕震空区、地震条带形成时段大致相当;空间上主要分布在祁连山构造带、东昆仑构造带、西秦岭构造带、南北构造带及天山构造带。远场前兆异常与空区图像的时空演变有较好的互补性和关联性,文中讨论了两者演化的有序性和阶段性与昆仑山口西8.1级地震孕育的时空过程。

关键词: 昆仑山口西8.1级地震, 地震图像, 地震空区, 远场前兆异常