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Reported investments in earthquake mitigation top $73 to $80 billion in the San Francisco Bay Area, California, since the 1989 Loma Prieta earthquake
Abstract and Figures
The purpose of this report is to provide a compilation of structural retrofits and replacements of older buildings in the San Francisco Bay Area that have either been completed since 1989 or that are in progress as of October 2018. For the purposes of this report, all or parts of nine Bay Area counties were included: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma. Santa Cruz County was not included. In total, we have identified $73 to $80 billion in investments to retrofit or replace structures to mitigate the impacts of future San Francisco Bay Area earthquakes. These totals represent an average investment of $2.5 to $2.8 billion per year in retrofits and replacement of structures since 1989. The compilation of 700 investments is presented as a table in the appendix. We consider this table as version 1, as we urge that those familiar with additional projects contact the report authors with information to update the table.
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Data
October 2018
... The result showed physical damage was critical for business operations and had a significant impact on business closure and relocation. Brocher et al. (2018) provided a compilation of structural retrofits and replacements of older buildings for all or parts of 9 counties in the San Francisco Bay Area that either had been completed since 1989 or that were in progress as of October 2018. They identified $73-80 billion in investments to retrofit or replace structures to mitigate the impacts of future San Francisco Bay Area earthquakes, which represented an average investment of $2.5-2.8 billion per year. ...
Economic resilience in California to destructive earthquakes is considered as an indicator of regional sustainability. We measure the abnormal volatility in stock markets, during the 1989 Loma Prieta Earthquake and the 1994 Northridge Earthquake as a series, by event study of statistical model, auto regressive moving average (ARMA) and generalized auto regressive conditional heteroscedasticity (GARCH) of economic model, and long short-term memory (LSTM) of deep learning model. The test results show there is no effect on the whole market; the sectors of Basic Industries Companies, Capital Goods Companies and Energy Companies are more sensitive to destructive earthquakes; on the level of stocks, the test result of the statistical model fit that of the economic model with percentage over 50%, and the result of the deep learning model is different. The relation between the company headquarters of the affected stocks with macroseismic intensity is unclear; those located around San Francisco Bay are sensitive to destructive earthquakes in California.
The Mw 6.0 South Napa earthquake, which occurred at 10:20 UTC 24 August 2014 was the largest earthquake to strike the greater San Francisco Bay area since the Mw 6.9 1989 Loma Prieta earthquake. The rupture from this right‐lateral earthquake propagated mostly unilaterally to the north and up‐dip, directing the strongest shaking toward the city of Napa, where peak ground accelerations (PGAs) between 45%g and 61%g were recorded and modified Mercalli intensities (MMIs) of VII–VIII were reported. Tectonic surface rupture with dextral slip of up to 46 cm was observed on a 12.5 km long segment, some of which was along a previously mapped strand of the West Napa fault system, although the rupture extended to the north of the mapped Quaternary strand. Modeling of seismic and geodetic data suggests an average coseismic slip of 50 cm, with a maximum slip of about 1 m at depths of 10–11 km. We observed up to 35 cm of afterslip along the surface trace in the week following the mainshock, primarily along the southern half of the surface rupture that experienced relatively little coseismic offset. Relocation of the sparse aftershock sequence suggests en echelon southwest‐ and northeast‐dipping fault planes, reflective of the complex fault geometry in this region. The Napa basin and historic and late Holocene alluvial flood deposits in downtown Napa amplified the ground motions there. Few ground failures were mapped, reflecting the dry season (as well as a persistent drought that had lowered the groundwater table) and the short duration of strong shaking in the epicentral area.
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