Determination of focal depth by two waveformbased methods: A case study for the 2008 Panzhihua earthquake

Abstract

With the 2008 MS6.1 Panzhihua earthquake as a case study, we demonstrate that the focal depth of the main shock can be well constrained with two approaches: (1) using the depth phase sPL and (2) using full waveform inversion of local and teleseismic data. We also show that focal depths can be well constrained using the depth phase sPL with single broadband seismic station. Our study indicates that the main shock is located at a depth of 11 km, much shallower than those from other studies, confirming that the earthquake occurs in upper crust. Aftershocks are located in the depth range of 11-16 km, which is consistent with a ruptured near vertical fault whose width is about 10 km, as expected for an MS6.1 earthquake.

近远震波形反演2013年芦山地震震源参数

“…中等强度及以上地震能够被全球台网所记录, 因此可以利用远震数据对震源机制解和深度进行研 究. 对于远震波形, 利用由 CAP 发展而来的 CAPtele 方法反演了震源机制解和矩心深度 [15,17] . 由于远震 面波走过的距离远远大于近震距离, 并且积累了地 壳路径上的结构效应, 面波往往变得很复杂.…”

Depth Determination of the 2010 El Mayor‐Cucapah Earthquake Sequence (M ≥ 4.0)

“…Because differential travel times between regional depth phases and their reference phases are most sensitive to the local structure above the hypocenter, uncertainty in estimated focal depth is on the same order as that of the velocity model. Previous studies have used various regional depth phases to determine focal depth, including depth phases of the direct P phase at small epicentral distance, for example, <100 km (e.g., Langston, 1987;Ma, 2010;Wang et al, 2011), depth phases of PmP and SmS (P and S wave reflections from the top of the Moho) at slightly larger distance, for example, 100-300 km (e.g., Helmberger et al, 1992;Ma, 2010), and depth phases of Pn (P wave bottoming in the uppermost mantle) at even larger distance, for example, >200 km (e.g., Husebye et al, 2013;Zonno & Kind, 1984). A major challenge of using regional depth phases comes from the complexity of regional waveforms.…”