Improving Estimation of the Magnitude of Historical California Earthquakes using IPEs
Session: Probabilistic Seismic Hazard Assessment: Where Do We Go from Here? [Poster]
Type: Poster
Date: 4/20/2021
Presentation Time: 11:30 AM Pacific
Description:
Estimating the magnitude of moderate to large historical earthquakes is crucial for assessing seismic hazard. These magnitudes are determined using instrumental records, field observations of fault slip, and/or the observed distribution of shaking intensity. However, instrumental data for earthquakes occurring in California prior to the 1960s were limited by a lack of nearby seismic stations and field observations of fault slip were often sparse or even nonexistent, making magnitude estimates for moderate to large historical earthquakes challenging and often uncertain. Using the new California Historical Intensity Mapping Project (CHIMP) dataset, we can better constrain magnitude estimates for these earthquakes by comparing their re-evaluated intensity distributions to those predicted by intensity prediction equations, or IPEs. This approach has become standard practice when instrumental and field data are limited or lacking. However, two first-order questions remain: (1) Which IPEs should be used to estimate magnitude? (2) How should we fit intensity data to an IPE? By comparing four commonly used IPEs to “Did You Feel It?” (DYFI) intensity distributions from moderate to large California earthquakes since 2000, which have well-constrained instrumental magnitudes, we find that no IPE significantly outperforms the others in fitting the intensity distributions or in estimating the earthquakes' magnitudes. We also find that logarithmic data binning, the most commonly used method to fit IPEs to intensity data, significantly influences the resulting magnitude estimates based on the arbitrary number of data bins chosen. These biases are especially apparent when binning intensity distributions from historical earthquakes, which often have a limited number of intensity observations available.
Presenting Author: Madeleine C. Lucas
Student Presenter: Yes
Authors
Madeleine Lucas Presenting Author Corresponding Author mlucas12@uw.edu University of Washington |
Leah Salditch leah@earth.northwestern.edu Northwestern University |
Molly Gallahue mollygallahue2023@u.northwestern.edu Northwestern University |
Susan Hough hough@usgs.gov U.S. Geological Survey |
James Neely james@earth.northwestern.edu Northwestern University |
Norman Abrahamson abrahamson@berkeley.edu University of California, Berkeley |
Seth Stein s-stein@northwestern.edu Northwestern University |
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Improving Estimation of the Magnitude of Historical California Earthquakes using IPEs
Category
Probabilistic Seismic Hazard Assessment: Where Do We Go from Here?