5:30 PM - 5:45 PM
[J09-2-05] ISC-EHB: Reconstructing the EHB Earthquake Database
The EHB database was originally developed with procedures described by Engdahl, Van der Hilst & Buland (1998), and it currently ends in 2008. It is a widely used seismological dataset, which we aim to expand and recreate, partly by exploiting the updated procedures at the International Seismological Centre (ISC), to produce the ISC-EHB. We begin with events in the modern period (2000-2014) and apply new and more rigorous procedures for event selection, data preparation, processing, and relocation.
The ISC-EHB criteria selects seismic events from the ISC Bulletin which have more than 15 teleseismic (> 28º) time defining stations, with a secondary teleseismic azimuth gap of < 180º, and a prime magnitude >3.75 (Di Giacomo & Storchak, 2016). These criteria minimize the location bias produced by 3D Earth structure, and select many events that are relatively well located in any given region.
There are several processing steps; (1) EHB software relocates all the events using ISC starting depths; (2) Near station and secondary phase arrival residuals are reviewed and a depth is adopted or assigned according to best fit, and in some instances depths may be reassigned based on other sources (e.g., USGS broadband depths); (3) All events are relocated with their new depths and plotted in subduction zone cross sections, along with events from the ISC-GEM catalogue for comparison; (4) These plots are used to confirm or modify weakly constrained depths.
The new ISC-EHB database will be useful for global seismicity studies and high-frequency global tomographic inversions. This will be facilitated by online access to the ISC-EHB Catalogue and Bulletin via the ISC, and will include maps and cross sections of the seismicity in subduction zones. Example maps and cross sections for events in years 2000-2003 will be presented.
The ISC-EHB criteria selects seismic events from the ISC Bulletin which have more than 15 teleseismic (> 28º) time defining stations, with a secondary teleseismic azimuth gap of < 180º, and a prime magnitude >3.75 (Di Giacomo & Storchak, 2016). These criteria minimize the location bias produced by 3D Earth structure, and select many events that are relatively well located in any given region.
There are several processing steps; (1) EHB software relocates all the events using ISC starting depths; (2) Near station and secondary phase arrival residuals are reviewed and a depth is adopted or assigned according to best fit, and in some instances depths may be reassigned based on other sources (e.g., USGS broadband depths); (3) All events are relocated with their new depths and plotted in subduction zone cross sections, along with events from the ISC-GEM catalogue for comparison; (4) These plots are used to confirm or modify weakly constrained depths.
The new ISC-EHB database will be useful for global seismicity studies and high-frequency global tomographic inversions. This will be facilitated by online access to the ISC-EHB Catalogue and Bulletin via the ISC, and will include maps and cross sections of the seismicity in subduction zones. Example maps and cross sections for events in years 2000-2003 will be presented.