Complimenting global earthquake locations at the ISC with full waveform depth constraints

Tom Garth*1,2, Karin Sigloch1, Dmitry A. Storchak2

1Department of Earth Sciences, University of Oxford, UK. (Email:, 2International Seismology Centre, Thatcham, UK

In the absence of nearby seismic networks, the depth resolution of global earthquake catalogues (such as the ISC, and ISC-EHB bulletins) is largely dependent on depth phases that have reflected from the earth’s surface (e.g. pP, sP). This gives extremely good depth resolution to deep and intermediate depth earthquakes (70 – 700 km). However, for shallow (< 40km) earthquakes the depth phases arrive only a few seconds after the first arrival. For events large enough to be reliably located teleseismically this often means that the depth phases are subsumed into the apparent source time function, and cannot easily be picked by an analyst. In order to use these indirect phases to constrain the depth of shallower events, the source time function and mechanism of the earthquake must be estimated. We explore the depth resolution that can be gained by considering relatively high frequency (~ 0.01–1 Hz) teleseismic P and SH arrivals. The earthquake mechanism, source time function and depth are constrained using a probabilistic inversion scheme (Stähler & Sigloch 2014; 2016). This technique makes use of the wealth of seismic waveform data and the increased availability of computational resources to provide insights on the full range of trade-offs between the earthquake mechanism, STF and event depth. Using these methods we hope to establish a reviewed data set of waveform depths and earthquake parameters at the ISC, with full uncertainty estimates enabling a global view of likely earthquake scenarios.