The distribution of modified mercalli intensity in the 18 April 1906 San Francisco earthquake
By: J. Boatwright and H. Bundock
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Abstract
We analyze Boatwright and Bundock's (2005) modified Mercalli intensity (MMI) map for the 18 April 1906 San Francisco earthquake, reviewing their interpretation of the MMI scale and testing their correlation of 1906 cemetery damage with MMI intensity. We consider in detail four areas of the intensity map where Boatwright and Bundock (2005) added significantly to the intensity descriptions compiled by Lawson (1908). We show that the distribution of off-fault damage in Sonoma County suggests that the rupture velocity approached the P-wave velocity along Tomales Bay. In contrast, the falloff of intensity with distance from the fault appears approximately constant throughout Mendocino County. The intensity in Humboldt County appears somewhat higher than the intensity in Mendocino County, suggesting that the rupture process at the northern end of the rupture was relatively energetic and that there was directivity consistent with a subsonic rupture velocity on the section of the fault south of Shelter Cove. Finally, we show that the intensity sites added in Santa Cruz County change the intensity distribution so that it decreases gradually along the southeastern section of rupture from Corralitos to San Juan Bautista and implies that the stress release on this section of rupture was relatively low.
Suggested Citation
Boatwright, J., Bundock, H., 2008, The distribution of modified mercalli intensity in the 18 April 1906 San Francisco earthquake, in Bulletin of the Seismological Society of America, v. 98, no. 2, p. 890-900, https://doi.org/10.1785/0120060404.
| Publication type | Conference Paper |
|---|---|
| Publication Subtype | Conference Paper |
| Title | The distribution of modified mercalli intensity in the 18 April 1906 San Francisco earthquake |
| DOI | 10.1785/0120060404 |
| Volume | 98 |
| Issue | 2 |
| Year Published | 2008 |
| Language | English |
| Larger Work Title | Bulletin of the Seismological Society of America |
| First page | 890 |
| Last page | 900 |