Forecasting the Impact of Tsunamis from the Alaska-Aleutian Subduction Zone in Southern California Under Rising Sea Levels

Session: Understanding Non-Traditional Seismic Tsunami Hazards
Type: Oral
Date: 4/28/2020
Time: 02:45 PM
Room: 120 + 130
Description: 

Although the amplification of storm- and tide-driven flooding frequency under future relative sea-level rise (RSLR) is well documented, the impact of RSLR on less commonly considered coastal hazards such as distant-source tsunamis remains poorly constrained. Here, we explore how RSLR over the next century will influence future tsunami flood heights at the Ports of Los Angeles and Long Beach in southern California, a region exposed to destructive tsunamis from the Alaska-Aleutian subduction zone. We use deterministic modeling of earthquake sources, ranging from M_w8.0 to M_w9.4, that might occur along the Semidi and Kodiak sections of the Alaska-Aleutian subduction zone to generate a dataset of possible distant-source tsunamis that may impact southern California. We then incorporate local probabilistic RSLR projections for both low and high greenhouse-emissions pathways (Representative Concentration Pathways [RCPs] 2.6 and 8.5, respectively) for the Ports of Los Angeles and Long Beach into our tsunami simulations. Earthquake and tsunami modeling combined with local probabilistic RSLR projections show the increased potential for low magnitude earthquakes to produce distant-source tsunamis that exceed historically observed flood heights (~1 m). At present sea level, a M_w 9.0 earthquake in the Alaska-Aleutian subduction zone is required to produce a > 1 m tsunami in southern California. Under RSLR projections for a high-emissions pathway (RCP8.5), this threshold would drop to M_w 8.0 by the year 2100, a magnitude that occurs ~6 times more frequently along the Alaska-Aleutian subduction zone.

Presenting Author: Tina Dura

Authors