P波初动包络线增长率区域特征的初步讨论

A Preliminary Study on Regional Characteristics of the Slope of the Initial Part of P-Wave Envelope

使用B-Δ方法对日本东北地区265个地震事件进行分析,得到该地区P波初动包络线增长率,研究其区域差异特性。利用P波初动2~3s的数据,通过经验公式预测地震震中距;通过对P波初动波形拟合公式Bt·exp(-At)得到拟合参数A和B;在确定公式斜率值后,得到经验系数c值。结果显示,该地区记录到的地震波P波包络线增长率存在一定的深度依赖性,深度较小的地震得到较小的c值,即表现出较为平缓的P波包络线增长率;深度较大的地震得到较大的c值,即表现出较为陡峭的P波包络线增长率。

We investigate the regional characteristics of the slope of the initial part of the P-wave enve- lope, which is used to determine epicentral distances in the Japan Meteorological Agency and Japan Railway Company earthquake early warning （EEW） systems. The Tohoku region is chosen as the study region. 265 events are collected. By fitting the function Bt · exp（-At） to the initial part of P- wave envelopes, we obtain sets of the parameters of A and B. Then, the intercepts of the above for- mula for each event are determined, keeping the slope to --2.27 to investigate the regional character- istics. Two tendencies emerge, shallow events have lower values of c, and deeper events have higher values of c.