甘肃测震台网监测能力及地震目录完整性分析

Analysis on the monitoring capability of seismic networks and completeness of earthquake catalogues in Gansu region

区域地震台网监测能力的科学评估,是进行区域地震活动性和地震危险性分析的重要基础,最小完整性震级Mc是表征台网监测能力的关键.本文以甘肃测震台网的地震观测报告和区域地震目录为基础资料,分析了甘肃及邻区地震监测能力在时、空上的分布特征,利用"震级-序号"法、"最大曲率"法(MAXC)、拟合度分别为90%和95%的拟合优度检验法(GFT)及"完整性震级范围"法(EMR)等,研究了甘肃区域地震目录最小完整性震级Mc的时、空分布特征.结果表明,1980年以来甘肃测震台网的地震监测能力得到了逐步提高,模拟记录时期和"九五"期间甘东南地区的地震监测能力明显高于祁连山地震带中西段,"十五"测震台网运行后,甘肃及邻区的地震监测能力的空间差异明显缩小.最小完整性震级Mc和监测能力的时空分布特征具有较好的一致性.随着台网的改造,Mc逐步降低,"十五"台网运行后,甘肃及邻区的ML1.8以上地震基本完整.此外,还讨论了相关技术规范对区域台网地震目录的影响,并且提出了消除该影响的科学途径和有效方法.该研究结果可为甘肃及邻区地震活动性分析和地震危险性评价等相关研究提供参考.

The minimum magnitude of completeness （Me） in earthquake cata logues, which reflects the monitoring capability, plays an important role in studying seismicity and assessing seismic hazards. Based on the observation bulletins and earthquake catalogues in Gansu region, we analyzed temporal and spalial variation of seismic network monitoring capability by using magnitude order number, maximum curvature （MAX）, goodness-of-fit test （GFT） and entire magnitude range （EMR） methods. The results show that the monitoring capability has been significantly improved since 1980. The monitoring capability in the southeastern region of Gansu was considerably better than that in Qilian seismic belt during the ＂analog＂ recording period and the ＂9th Five-Year Plan＂ period. During the ＂10th Five-Year Plan＂ period （2001--2005）, the spatial differences in earthquake monitoring capability near Gansu and its adiaeent areas were significantly decreased. The spatial and temporal distribution of M,- is consistent with that of the monitoring capability. With the upgrading of seismic stations, the minimum magnitude is gradually lowered. M~ could reach as low as ME1.8 in Gansu and its adjacent areas during the ＂lOth Five-Year Plan＂ period. In addition, we also discuss the effect of relevant provisions on regional earth- quake catalogues and propose a way to eliminate the effect. The results can provide references for analyzing seismic activity and assessing seismic hazards in this region.