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Chapter 1
Introduction
Rapid development in California in the past thirty years and the size of economy so
dependent on ports and harbor for trade, necessitates quantitative studies of tsunami
hazard in California.
In the past 110 years, California has experienced seven substantial tsunamis; i.e., the
1896 Sanriku Japan, 1946 East Aleutians (Unimak), 1952 Kamchatka, 1957 Aleutians,
1960 Chile, 1964 Alaska and 1975 Hawaii tsunamis. The 1896 Great Meiji earthquake
along the Sanriku trench triggered a wave locally running up 38m killing 26,000 people
(Lander et al., 1993). The tsunami reached 1.5m and caused damage at Santa Cruz, Cal-ifornia
(Soloviev and Go, 1974). The 1946 Aleutian earthquake (Mw # 8.6; Lopez and
Okal, 2006) not only destroyed the lighthouse at Scotch Cap on Unimak Island, but also
generated a devastating tsunami that killed 173 in Hawaii with 17m runup (Okal et al.,
2003). The Pacific Tsunami Warning Center was established in response to this event.
The 1952 Kamchatka and 1957 Aleutian tsunamis were also noticed, the latter damag-ing
San Diego Harbor (Soloviev and Go, 1974). The 1960 Mw # 9.5 Great Chilean
event, featuring the largest seismic moment ever recorded instrumentally, was caused
by the rupture of 1, 000km long 150km wide segment with an average displacement
around 20m (Plafker, 1972). These earthquakes and the subduction zones in Japan,
Kuril Islands (KSZ), Alaska-Aleutians (AASZ), Cascadia (CSZ) and South America–
Chile (SASZ) are shown in figure 1.1.
1
Object Description
| Title | Deterministic and probabilistic tsunami studies in California from near and farfield sources |
| Author | Uslu, Burak |
| Author email | uslu@usc.edu; burak.uslu@noaa.gov |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Civil Engineering |
| School | Viterbi School of Engineering |
| Date defended/completed | 2007-09-21 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-10-30 |
| Advisor (committee chair) | Synolakis, Costas E. |
| Advisor (committee member) |
Bardet, Jean-Pierre Okal, Emile A. Moore, James Elliott, II |
| Abstract | California is vulnerable to tsunamis from both local and distant sources. While there is an overall awareness of the threat, tsunamis are infrequent events and few communities have a good understanding of vulnerability. To quantitatively evaluate the tsunami hazard in the State, deterministic and probabilistic methods are used to compute inundation and runup heights in selected population centers along the coast.; For the numerical modeling of tsunamis, a two dimensional finite difference propagation and runup model is used. All known near and farfield sources of relevance to California are considered. For the farfield hazard analysis, the Pacific Rim is subdivided into small segments where unit ruptures are assumed, then the transpacific propagations are calculated. The historical records from the 1952 Kamchatka, 1960 Great Chile, 1964 Great Alaska, and 1994 and 2006 Kuril Islands earthquakes are compared to modeled results. A sensitivity analysis is performed on each subduction zone segment to determine the relative effect of the source location on wave heights off the California Coast.; Here, both time-dependent and time-independent methods are used to assess the tsunami risk. In the latter, slip rates are obtained from GPS measurements of the tectonic motions and then used as a basis to estimate the return period of possible earthquakes. The return periods of tsunamis resulting from these events are combined with computed waveheight estimates to provide a total probability of exceedance of given waveheights for ports and harbors in California. The time independent method follows the practice of past studies that have used Gutenberg and Richter type relationships to assign probabilities to specific tsunami sources.; The Cascadia Subduction Zone is the biggest nearfield earthquake source and is capable of producing mega-thrust earthquake ruptures between the Gorda and North American plates and may cause extensive damage north of Cape Mendocino, to Seattle. The present analysis suggests that San Francisco Bay and Central California are most sensitive to tsunamis originating from the Alaska and Aleutians Subduction Zone (AASZ). An earthquake with a magnitude comparable to the 1964 Great Alaska Earthquake on central AASZ could result in twice the wave height as experienced in San Francisco Bay in 1964.; The probabilistic approach shows that Central California and San Francisco Bay have more frequent tsunamis from the AASZ, while Southern California can be impacted from tsunamis generated on Chile and Central American Subduction Zone as well as the AASZ. |
| Keyword | assessment; California; hazard; model; probability; tsunami |
| Geographic subject | capes: Kamchatka; islands: Kuril Islands; fault zones: Cascadia Subduction Zone |
| Geographic subject (state) | California; Alaska |
| Geographic subject (country) | Chile |
| Coverage date | 1952/2008 |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1706 |
| Contributing entity | University of Southern California |
| Rights | Uslu, Burak |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-uslu-2434 |
| Archival file | uscthesesreloadpub_Volume40/etd-uslu-2434.pdf |
Description
| Title | Page 16 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Chapter 1 Introduction Rapid development in California in the past thirty years and the size of economy so dependent on ports and harbor for trade, necessitates quantitative studies of tsunami hazard in California. In the past 110 years, California has experienced seven substantial tsunamis; i.e., the 1896 Sanriku Japan, 1946 East Aleutians (Unimak), 1952 Kamchatka, 1957 Aleutians, 1960 Chile, 1964 Alaska and 1975 Hawaii tsunamis. The 1896 Great Meiji earthquake along the Sanriku trench triggered a wave locally running up 38m killing 26,000 people (Lander et al., 1993). The tsunami reached 1.5m and caused damage at Santa Cruz, Cal-ifornia (Soloviev and Go, 1974). The 1946 Aleutian earthquake (Mw # 8.6; Lopez and Okal, 2006) not only destroyed the lighthouse at Scotch Cap on Unimak Island, but also generated a devastating tsunami that killed 173 in Hawaii with 17m runup (Okal et al., 2003). The Pacific Tsunami Warning Center was established in response to this event. The 1952 Kamchatka and 1957 Aleutian tsunamis were also noticed, the latter damag-ing San Diego Harbor (Soloviev and Go, 1974). The 1960 Mw # 9.5 Great Chilean event, featuring the largest seismic moment ever recorded instrumentally, was caused by the rupture of 1, 000km long 150km wide segment with an average displacement around 20m (Plafker, 1972). These earthquakes and the subduction zones in Japan, Kuril Islands (KSZ), Alaska-Aleutians (AASZ), Cascadia (CSZ) and South America– Chile (SASZ) are shown in figure 1.1. 1 |
