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Deterministic and Probabilistic Tsunami Studies in ....

Deterministic and Probabilistic Tsunami Studies in California from near and Farfield SourcesBy: Burak Uslu
Ph. D. Candidate
Oral DefenseAbstract:The state California is vulnerable to tsunamis from both local and distant sources. While there is awareness of the threat, tsunamis are infrequent and few communities have a good understanding of vulnerability. To evaluate the tsunami threat, deterministic and probabilistic methods are used to compute inundation and runup heights. 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, the Pacific Rim is subdivided into small segments where unit ruptures are assumed. The historical records from the 1952 Kamchatka, 1960 Great Chile, 1964 Great Alaska, and 1994 and 2006 Kuril Islands Earthquakes are compared to the modeled results. A sensitivity analysis is performed on each subduction zone segment to determine the effect of the source location on wave heights off the California Coast.Earlier studies employed a time-dependent method based on a Richter and Gutenberg type relationship, and assigned probabilities on each subduction zone depending on previous surveys. Time-dependent and time-independent methods are used in this study. In the latter, the slip rates are obtained from GPS measurements of the tectonic plates and used as a basis to get the return period of each possible earthquake. The return periods of the tsunamis resulting from these events are combined with the wave height exceedance from the numerical results to provide a total probability of exceedance, for ports and harbors in California. The Cascadia Subduction Zone, a portion of which is located in the boundaries of California and is capable of producing mega-thrust earthquake rupture between Gorda and North American plate, may cause large damage north of Cape Mendocino. Northern California is likely to have the biggest damage from a Cascadia rupture. The sensitivity analysis suggests that San Francisco Bay and Central California exhibits the largest impact 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 damage as experienced by SF Bay in the 1964 event.The probabilistic approach shows that Central California and San Francisco Bay have more frequent tsunamis, as they are oriented towards the AASZ; while Southern California can be impacted from tsunamis generated on Chile and Central American Subduction Zone as well as the AASZ.

Location: Kaprielian Hall (KAP) - rielian Hall 209

Audiences: Everyone Is Invited

Contact: Evangeline Reyes