Two Earthquake Foreshock Sequences Post Gulia and Wiemer (2019)

Session: Early Results from the 2020 M6.4 Indios, Puerto Rico Earthquake Sequence
Type: Oral
Date: 4/30/2020
Time: 10:45 AM
Room: 115
Description: 

Recognizing an earthquake as a foreshock in real-time would provide useful forecasting capabilities. In a recent study, Gulia and Wiemer (2019) suggested a stop-light system that relies on abrupt changes in b-values providing a measurable attribute to distinguish foreshock from aftershock sequences. The recent earthquake foreshock sequences in Ridgecrest, California and Ilios, Puerto Rico, provide an opportunity to put the method, as specified, to the test. We reproduce the analysis of Gulia and Wiemer (2019) for these two sequences. For Ridgecrest, the b-value time series may have indicated an elevated risk of a larger impending earthquake after the M_WW6.4 foreshock and correctly identifies the onset of the aftershock sequence. In the case of the earthquake sequence south of Ilios, Puerto Rico, we find significant drops in b-value during the foreshocks leading up to the mainshock, which has not yet (28 January 2020) recovered to background levels. In applying the procedure to two recent sequences, the Ridgecrest sequence generally conforms to expectations, whereas the Puerto Rico sequence will only do so if a larger event occurs in the future with an ensuing b-value increase. Practical barriers to any implementation of this approach are well-calibrated maps of regionalized background b-values and consistent (versioned) low completeness catalogs during sequences, which requires, dense instrumentation and systematic catalog production.

Presenting Author: Kelian Dascher-Cousineau

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