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A New Earthquake Recurrence Model That Better Reflects the Strain Accumulation and Release Processes That Produce Earthquakes

Description: 

Current earthquake recurrence models have two major limitations. First, they predict that the
probability of a large earthquake stays constant or even decreases after it is “overdue” (past the
expected average recurrence interval), so additional accumulated strain does not make an
earthquake more likely. Second, the models assume that large earthquakes release all
accumulated strain, despite evidence of partial strain release in earthquake histories showing
clusters and gaps. These limitations arise because the models are purely statistical, assuming that
future earthquakes will satisfy a probability distribution that describes the times between past
large earthquakes. These models describe average earthquake behavior, but not deviations from
it, because they do not incorporate fundamental aspects of the strain accumulation and release
processes that cause earthquakes.

Here we calculate earthquake probabilities using our Generalized Long-Term Fault Memory
(GLTFM) model, which better reflects the strain accumulation and release processes. Our model
assumes that earthquake probability always increases with time between earthquakes and allows
the possibility of partial strain release. We apply this model to different faults including the
southern San Andreas fault. By allowing partial strain release, GLTFM incorporates the specific
timing of past earthquakes, which commonly used probability models cannot do, so it better
forecasts the short inter-event time preceding the 1857 Ft. Tejon earthquake. Looking to the
future, current models estimate the earthquake probability on the southern SAF will be
essentially unchanged in the next 80 years, but GLTFM predicts that the probability will
continue to grow, resulting in a 30-year earthquake probability approximately 60% higher than
the other models. These forecast differences could have major implications for hazard
assessment.

Session: Opportunities and Challenges in Source Modeling for Seismic Hazard Analysis

Type: Oral

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: James S. Neely

Student Presenter: No

Invited Presentation: No

Authors