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Mendocino all the way south to Pt. Conception has greater tsunami hazard from the
Eastern Aleutians or Alaska (ASSZ). The sensitivity study in Chapter 2, carried out
using NOAA’s FACTS database, showed that the central California tsunami responses
were higher for tsunamis from AASZ earthquakes than from other sources and may
experience a larger hazard than in 1964. Even though an extreme event from the south-ern
end of the CSZ is a cause of concern, locally in the Pacific Northwest Section 2.4
shows that the tsunami waves radiate away from the California coast.
Modeled and historical farfield tsunamis are smaller in amplitude in southern Cal-ifornia
than the rest of the state. This is partially because of its orientation towards
the mid–Pacific, its distance from the AASZ, and the complex offshore geography of
the Channel and Santa Catalina islands. However, the sensitivity study in Chapter 2
computed that tsunamis from Peru and Chile Subduction Zones (SASZ) are as danger-ous
as they are from AASZ. The offshore fault lines in southern California also pose a
threat to trigger moderately hazardous tsunamis for ports as well. The biggest danger
in southern California is from the submarine landslides from offshore canyons around
Redondo, Palos Verdes and Santa Barbara (Borrero et al., 2001; Borrero, 2002; Borrero
et al., 2004b).
4.2 Probabilistic Farfield Tsunami Predictions in Cali-fornia
Probabilistic hazard modeling was performed first at seven offshore locations as shown
in Figure 3.6, and then later at tide gauge locations at Crescent City, San Francisco and
Los Angeles Harbor. The return periods of individual events are calculated with two
153
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 168 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Mendocino all the way south to Pt. Conception has greater tsunami hazard from the Eastern Aleutians or Alaska (ASSZ). The sensitivity study in Chapter 2, carried out using NOAA’s FACTS database, showed that the central California tsunami responses were higher for tsunamis from AASZ earthquakes than from other sources and may experience a larger hazard than in 1964. Even though an extreme event from the south-ern end of the CSZ is a cause of concern, locally in the Pacific Northwest Section 2.4 shows that the tsunami waves radiate away from the California coast. Modeled and historical farfield tsunamis are smaller in amplitude in southern Cal-ifornia than the rest of the state. This is partially because of its orientation towards the mid–Pacific, its distance from the AASZ, and the complex offshore geography of the Channel and Santa Catalina islands. However, the sensitivity study in Chapter 2 computed that tsunamis from Peru and Chile Subduction Zones (SASZ) are as danger-ous as they are from AASZ. The offshore fault lines in southern California also pose a threat to trigger moderately hazardous tsunamis for ports as well. The biggest danger in southern California is from the submarine landslides from offshore canyons around Redondo, Palos Verdes and Santa Barbara (Borrero et al., 2001; Borrero, 2002; Borrero et al., 2004b). 4.2 Probabilistic Farfield Tsunami Predictions in Cali-fornia Probabilistic hazard modeling was performed first at seven offshore locations as shown in Figure 3.6, and then later at tide gauge locations at Crescent City, San Francisco and Los Angeles Harbor. The return periods of individual events are calculated with two 153 |
