一、引言1982年6月16日甘孜发生M=6.0级地震以来,四川省内已四年无M≥5.0级的地震.这样长时间的平静是否意谓着异常?对这一多方关注的问题,本文就地震活动的历史记载进行探索对资料的取用按以下约定:1)地区范围:对南北地震带的分段有多种意见.通常对南北带中段有以下不同的划定法:(1)四川省行政区范围内105°E以西部分;(2)27°～34°N,99°～105°E这个范围;(3)27°-33°N,99°-105°E所定的范围连同小江带北段及永胜、华坪地区,在文献[1]中年最大震级分布拟合表明第二种划定法比起(1)与(3)更符合地震活动的某些内在规 I. INTRODUCTION Since the M = 6.0 earthquake in Garzi on June 16, 1982, there have been no earthquakes of magnitude M≥5.0 in Sichuan Province for four years. Does this prolonged calm mean an anomaly? In this paper, the historical records of seismic activity are explored. The access to data is based on the following conventions: 1) Regional scope: There are several opinions on the subdivision of the north-south seismic zone, and the following different demarcation laws are usually applied to the middle section of the north- (1) west of 105 ° E within the administrative region of Sichuan Province; (2) this range of 27 ° -34 ° N and 99 ° -105 ° E; (3) 27 ° -33 ° N, 99 ° -105 ° E The distribution of the maximal magnitude distribution in the mid-year of [1] shows that the second delineation method is more consistent with some of the seismic activities than (1) and (3) Internal rules