云南腾冲地区三维地震定位

Probabilistic earthquake location in three-dimensional velocity models applied in Tengchong

本文利用中国数字测震台网和流动台站的地震资料,基于参数优化的AICD自动拾取算法和质量评估方案得到了高质量的震相到时,并在此基础上使用一维、三维定位方法对腾冲地区的799次地震事件进行了重新定位。定位结果显示:水平方向上,一维、三维重定位结果相差较小;深度方向上,三维定位的震源成丛分布比一维定位结果更加密集,地震主要位于地壳内低速层之上。分别利用一维、三维定位方法对典型地震、人工震源进行定位,结果表明,三维定位的精度明显优于一维定位,其在水平、深度方向上的平均绝对定位误差分别为0.7 km和1.3 km。

The accuracy of earthquake location strongly depends on quality and consistency of available traveltime data.We obtained accurate automatic picks by employing optimized AICD automatic pickers and quality assessment scheme at temporary and permanent seismic networks surrounding Tengchong volcanic area.Based on those high-quality first-arrivals,we relocated 799 earthquakes with 1 D(Hypomat)and 3 D(probabilistic earthquake location)location algorithms.The comparison of 799 hypocenter relocations obtained by 1 D location method(Hypomat)to those relocated in 3 D velocity model using a probabilistic approach reveals no systematic shifts in epicenter locations but does exhibit large vertical shifts.3 D relocations are usually at the top of low velocity layers in crust and more clustered than 1 D relocations.The events relocated with the 1 D model seem often deeper than the events relocated with the 3 D model.Relocating artificial sources and typical seismic sequences using 1 D and 3 D methods confirms that probabilistic earthquake location combined with 3 D velocity model yields more precise hypocenter locations for Tengchong and has mean absolute errors of 0.7 km horizontally and 1.3 km vertically.