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wide and no where deeper than 30m. Wentworth et al. (1997) mapped the landslide
hazard and found the bathymetry unable to pose a tsunami hazard compared to other
sources examined in this study.
Earthquake surface waves are known to produce seiches in closed bodies of water
and bays (Raichlen, 1966; Ruscher, 1999; Rueda and Schladow, 2002; Barberopoulou
et al., 2004; Synolakis, 2003). The large amplitude surface waves are believed ampli-fied
by basin geometry, exciting water oscillations or seiches. To produce significant
seiching in a body of water, the forcing periods must be close to the natural period of
bay or of an overtone. The typical characteristic periods for San Francisco Bay range
from 30–45 minutes and are much longer than surface wave periods; thus, non-tsunami
induced seiches in San Francisco Bay are not considered to pose a hazard comparable
to the other sources modeled in this study.
2.3 Using MOST to Simulate Historical Events
To check the validity of our model and method, we compare results of the simulation
of historical events to its available instrumental records from tide gauges at various
locations along the California coast.
2.3.1 Comparison to Historical Measurements from the 1960
Chilean tsunami
Figure 2.8 shows a comparison between modeled and recorded waveheights for the 1960
Chilean tsunami at several locations in California. The modeled results agree well with
the observed data in terms of amplitude and period. There is a discrepancy in the mod-eled
arrival time, which is only about 7 minutes and thus negligible when compared to
59
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 74 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | wide and no where deeper than 30m. Wentworth et al. (1997) mapped the landslide hazard and found the bathymetry unable to pose a tsunami hazard compared to other sources examined in this study. Earthquake surface waves are known to produce seiches in closed bodies of water and bays (Raichlen, 1966; Ruscher, 1999; Rueda and Schladow, 2002; Barberopoulou et al., 2004; Synolakis, 2003). The large amplitude surface waves are believed ampli-fied by basin geometry, exciting water oscillations or seiches. To produce significant seiching in a body of water, the forcing periods must be close to the natural period of bay or of an overtone. The typical characteristic periods for San Francisco Bay range from 30–45 minutes and are much longer than surface wave periods; thus, non-tsunami induced seiches in San Francisco Bay are not considered to pose a hazard comparable to the other sources modeled in this study. 2.3 Using MOST to Simulate Historical Events To check the validity of our model and method, we compare results of the simulation of historical events to its available instrumental records from tide gauges at various locations along the California coast. 2.3.1 Comparison to Historical Measurements from the 1960 Chilean tsunami Figure 2.8 shows a comparison between modeled and recorded waveheights for the 1960 Chilean tsunami at several locations in California. The modeled results agree well with the observed data in terms of amplitude and period. There is a discrepancy in the mod-eled arrival time, which is only about 7 minutes and thus negligible when compared to 59 |
