青藏高原北部地区地震频度短期异常特征研究

STUDY ON SHORT-TERM ANOMALY CHARACTERISTICS OF SEISMIC FREQUENCY IN NORTHERN REGION OF QINGHAI-TIBET PLATEAU

摘要:

在青藏高原北部地区活动地块划分的基础上,以地块为研究单元,对1970年以来的小震频度进行了全时空扫描,以研究其短临时间特征.结果表明:虽然受地域和地质构造的影响,各地区小震频度的短临异常与5级地震的对应率不相同,但绝大多数地区的小震频度正、负异常的起始时间、最大(最小)值时间和结束时间均出现在中强地震前的1~6个月.对结果统计检验,本区R ≥ R_97.5%的合格率为69%,内、边邻地区合计R值合格率为94%.

Abstract:

Based on the division of active blocks in northern Qinghai-Tibet plateau, the full spatio-temporal scan for seismic frequency of small earthquakes in every blocks since 1970 is down to study short-impending anomaly characteristics.The result indicates that the corresponding ratios of the anomalies of seismic frequency to M_S ≥ 5.0 earthquakes are different in different blocks, owing to various regional tectonics, but the most of starting time, ending time and maximal (or minimal) value of positive and negative anomalies for small seismic frequency appeare one to six months before medium-strong earthquakes. And the result is checked up statistically by using R value, the eligibility rate(R ≥ R_97.5%) in the region is 69%, and the general Eligibility rate of R-value for inner and adjacent regions is 94%.