Source Parameters and Moment Magnitudes From Seismogram Envelopes – The Coda Calibration Tool

Session: Leveraging Advanced Detection, Association and Source Characterization in Network Seismology
Type: Oral
Date: 4/30/2020
Time: 04:45 PM
Room: 120 + 130
Description: 

The coda envelope method of obtaining source spectra described in Mayeda and Walter (1996) provides energy measures and moment magnitudes (M_w) for local to regional events from as few as one station.  The scattering of energy in the coda provides an azimuthally averaged view of the source, and the long envelope measurement provides a stable average like network averaging does.  These coda results are fairly insensitive to source and path heterogeneity.  The method allows for a consistent measure of M_w over a broad range of event sizes rather than relying on magnitude relationships between M_w derived from waveform modeling and various narrowband magnitudes such as M_L, M_D, m_b. A challenge to its more widespread usage has been the lack of good software to implement the method.  This is changing as we make progress on a Coda Calibration Tool (CCT).  The CCT stems from a multi-year collaboration between LLNL and the U.S. National Data Center (NDC) scientists with the goal of developing a fast and easy Java-based, platform independent, coda envelope calibration and processing tool.  We present an overview of the tool and advantages of the method along with several calibration examples, all of which are freely available to the public via GitHub (https://github.com/LLNL/coda-calibration-tool/releases). Once a region is calibrated, the tool can then be used in routine processing to obtain stable source spectra and associated source information (e.g., M_w, radiated seismic energy, apparent stress, corner frequency, source discrimination).  As more events are recorded or new stations added, simple updates to the calibration can be performed.  All calibration and measurement information is stored within an internal database that can be queried for future use.  We welcome future collaboration, testing and suggestions by the geophysical community.

Presenting Author: William R. Walter

Authors