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Community Stress Drop Validation Study using the 2019 Ridgecrest Earthquake Sequence

Stress drop is a fundamental earthquake source parameter that in theory relates the average slip on a fault to rupture area, and in practice characterizes the high frequency seismic radiation. It is a key parameter in earthquake ground motion modeling, rupture simulation, and analysis of source physics. However, stress drops are notoriously variable and difficult to measure; estimates by different researchers, using different methods or datasets, yield highly inconsistent values which may mask physical trends. We propose a Community Stress Drop Validation Study using the 2019 Ridgecrest Earthquake Sequence to understand and resolve differences in stress drop measurement, in which many researchers from the community independently calculate and submit stress drop estimates using a consistent dataset of the 2019 Ridgecrest sequence of earthquakes. Rachel Abercrombie and Annemarie Baltay are leading the effort, and have applied for SCEC TAG support. This study is just starting up, and NOW is the perfect time to get involved.

How to Participate Anyone is welcome and everyone is encouraged to join. You can download the data and perform analysis for stress drop. Corner frequency or other source parameters. You can become involved in the “meta-analysis”: comparing different results. You can just come to the workshop and see what’s going on! An upcoming SRL article will discuss the study in more detail. Sign up on the mailing listserv to stay aware of developments https://listserv.usgs.gov/mailman/listinfo/stressdrop-validation

Timeline: All events will be posted to the mailing list

  • April/May 2021: Distribute a common dataset, accessible here (and announced to email list). We invite any and all interested to analyze the dataset for stress drop (or other relevant source parameters).
  • August/September 2021: Initial (virtual) workshop in late summer 2021 to come together and discuss these results. Leading up to the workshop, we will ask participants to submit their analysis results and will begin some meta-analysis to compare them.
  • December 2021: AGU session

Datasets

Please cite the References when using these datasets.

Full dataset coming shortly, which comprises 12,943 events of M1+ over a two week span from July 4, 2019 through July 17, 2019 (Figures below).

 

Figures

Figure 1. Map of earthquakes included in the analysis, selected from Trugman (2020) relocated catalog. All events from start of July 4 2019 to end of July 17 2019, Magnitude>=1, colored (and symbol size) by SCSN catalog magnitude. Other earthquakes in the catalog (outside our time and magnitude selection) are shown in gray.
Figure 2. Histogram of the selected earthquakes with magnitude.
Figure 3. Magnitude distribution of the selected earthquakes in time.
Figure 4. Depth distribution of the selected earthquakes as a function of Magnitude, using Trugman (2020) relocations.

 

References

  • A Community Stress Drop Validation Study Using the 2019 Ridgecrest Earthquake Dataset. Baltay, A., Abercrombie, R. E., Taira, T. (2021), SSA Annual Meeting 2021.
  • Trugman, D. T. (2020), Stress‐Drop and Source Scaling of the 2019 Ridgecrest, California, Earthquake Sequence. Bulletin of the Seismological Society of America 2020; 110 (4): 1859–1871. doi: 10.1785/0120200009
  • Baltay, A. S., R. E. Abercrombie, T. Taira, A community stress drop validation study using the 2019 Ridgecrest Earthquake Sequence, Seismological Research Letters (in preparation)
  • To cite any data from SCEDC see SCEDC Citation Policy