震源区背景应力水平的区域特征及潜在地震震级的估计

REGIONAL VARIATION OF THE BACKGROUND STRESS AND THE ESTIMATION OF MAGNITUTE FOR THE POTENTIAL EARTHQUAKES

通过发生在全球不同区域内面波震级(或M_w)相同的浅源大地震的体波震级(?)_b、短周期(1—10秒)震源谱以及重复周期不同的地震的破裂长度的对比,可以得出大地震的应力降有明显的地区差异性:发生在板块边缘的地震,重复时间短而应力降低;板内大地震的重复时间长而应力降高,两者可相差5倍;此外,板内不同地区的大地震,比如中国东部和西部的地震,也存在差别。这一结果反映了不同震源区背景应力水平的差别,对于地震灾害的预测是重要的信息。 文中所给出的大地震的破裂长度与重复时间的关系,可用于某些仅能由地质学方法推断潜在断层长度及重复时间的地区估计潜在地震震级,或者已知震级估计重复时间,以进行灾害预测。

By comparing the body wave magnitutes mb, the short period (1 to 10 s) source spectra for the earthquakes with same Ms or Mw in different globle tectonic provinces and the rupture lengthes for the events with different repeat time, the following results are obtained: the stress drops of the events with shorter repaet time in the plate borders are smaller than those of the intraplate events with longer repeat time, the average difference is about 5 times. The re-gional variation also existes for the intraplate events, for example for those between the eas-tern part and the western part of China. All of the results suggest that the backgroud stress of the source region is different from each other, these results may be useful for the earth-quake hazard prognostication.We also provide a relationship between rupture length and repeat time, which can be used to estimate the earthquake magnitute for the potential fault with known roupture length and repeat time determined by the geological method or to estimate the repeat time for the known magnitute events.