1931年南海西沙群岛北6 3/4级地震震中位置与震级的讨论

摘要

Based on the seismogeological tectonic environment , the intensity record of historical earthquakes and so on, it is discussed on the epicenter and magni tude of the MS6 3/4 earthquake in the north of the Xisha I slands of South C hina Sea occurred on September 21,1931. This earthquake caused intensityⅤin Gu angzhou, Sanshui and Zhongshan , the long axis of isoseismic line with intensity about trends NW.According to the iso-intensity line roughly delineated,it is co njectured that the epicenter location should be moved 110 km to east (at 20°N, 114.1°E),and based on the statistical result of the maximum distance from the epicenter location to isoseismic line with intensityⅤ, the magnitude M S=7.1 of this earthquake determined by Xujiahui observatory in Shanghai should be more reasonable.%根据地震地质构造环境、历史地震烈度记录 等资料，对1931年9月21日南海西沙群岛北海中6 3/4级地震的震中位置和震级进行了讨 论。该次地震广州、三水、中山等地的烈度达5°，5°等震线长轴大体呈NW向。由大致 勾画 的等烈度线图推测，其震中位置应从现定微观震中向东推移110 km(20°N，114.1°E)。参 考我国6 3/4～7 1/2级地震的震中位置与V度等震线最远距离的统计结果，认为上 海徐家汇观象台将该震定为7.1级是较为合理的。