利用地震台阵识别中深源远震sP和pP震相确定震源深度

Determining the Focal Depth by Identifying Deep Teleseismic sP and pP Phases Using Seismic arrays

摘要:

震源深度是目前最难确定的震源参数之一,基于密集的近台观测数据可以准确确定近震震源深度,但对远震的震源深度无法较好地约束。远震反射波震相sP和pP包含用于确定震源深度的有效信息,理论上可以对远震的震源深度进行有效约束。将国内测震台站中台间距远小于震中距的区域台站作为台阵,通过互相关、震相对齐、波形叠加聚束等处理,可以提升sP和pP深度震相的信噪比。利用IASP91全球模型,根据震相走时差得到较为准确的震源深度。本文计算了2017—2020年M≥6.0的64个国外远震的震源深度。通过与GCMT、GFZ、USGS等机构给出的结果相比,验证了此方法得到的震源深度的可靠性。通过讨论破裂持续时间对pP震相识别的影响,得到此方法在矩震级6.0～8.5时,在不同深度上有较好的适用性。

Abstract:

Earthquake focal depth is currently one of the most difficult focal parameters to determine,The focal depth can be accurately determined based on dense near-station observation data,but the focal depth of teleseismic earthquakes cannot be well constrained. The teleseismic reflection phases sP and pP contain effective information for determining the focal depth,and theoretically,the focal depth of teleseismic waves can be effectively constrained. We use domestic seismic stations as well as stations in a certain province as a array,in ordr to improve the signal-to-noise ratio of sP and pP deep seismic phases by processing cross-correlation,seismic phase alignment,and waveform stacking. The IASP91 global model is used to obtain a more accurate focal depth according to the travel time of the seismic phase. In this paper we calculate the focal depths of 64 foreign teleseisms with M≥6 from 2017 to 2020. Compared with authoritative institutions such as GCMT,GFZ,and USGS,the focal depth obtained by this method is relatively reliable. By discussing the effect of rupture duration on pP phase identification,it is concluded that this method has good applicability at different depths when the moment magnitude is between 6～8.5.