Although the effects of large-magnitude earthquake scenarios in California have been studied
extensively, there are no regional scale studies performed for potential earthquake sequences
characterized by multiple major mainshocks in California or elsewhere in the world. Furthermore,
current seismic design codes do not explicitly account for the effects of earthquake consequences
nor their aftershocks.
Motivated by the recent domestic and international earthquake sequences with multiple
mainshocks, and the high consequences and estimated losses of forecasted earthquakes in
California, the objective of this study is to quantify regional scale consequences of two impactful
and plausible earthquake sequence scenarios, one in the San Francisco Bay Area (SFBA) and
another one in the Los Angeles Metropolitan Area (LAMA).
To achieve this objective, first the observations and lessons learned from historical earthquakes
with multiple mainshocks are documented, particularly with emphasis on implications for
California and relevant recommendations. These earthquakes include the 2023 Türkiye sequence,
the 2022/23 Ferndale earthquake sequence (including the 2022 Ferndale mainshock and the 2023
Rio Dell aftershock), the 2022 Iran earthquake sequence, 2022 Taiwan earthquakes, 2019
Ridgecrest earthquakes, Christchurch earthquake series of 2010 and 2011, and the 1999 Kocaeli
and Düzce, Türkiye earthquakes1.
The second part of the study is guided by the documentation in the first part and focuses on the
regional scale assessment of buildings in California in two scenario earthquakes. These two
scenario earthquakes, one for SFBA and the second one for LAMA, are both characterized by two
large magnitude mainshocks that occur in sequence. Following the analysis steps of the PEER
Performance-based Earthquake Engineering (PBEE) methodology, the regional scale assessment
comprises: (a) hazard analysis, (b) structural analysis, (c) damage analysis, including
compounding damage due to the earthquake sequence, and (d) loss analysis, and is conducted at
two levels. Level 1 assessment aims at quantifying the consequences (e.g., building damage states,
economic loss, casualties) for the entire region of interest using methods like the HAZUS
methodology. Level 2 assessment focuses on a more detailed assessment of several smaller regions
where the losses are expected to be the largest.
This Volume I report focuses on documenting the observations and lessons learned from historical
earthquakes with multiple mainshocks, implications for California, and relevant recommendations.
The conducted regional scale assessments will be presented in Volume II report.
Download full report: click here
Two-page summary: click here
Executive summary: click here
