The 1810 Loreto Tsunami Triggered by Submarine Landslide in the Gulf of California, Mexico - Historical Evidence and Numerical Modeling

Session: Understanding Non-Traditional Seismic Tsunami Hazards
Type: Oral
Date: 4/28/2020
Time: 04:30 PM
Room: 120 + 130
Description: 

Tsunami hazard caused by landslide-generated tsunamis has been underestimated. Even more, the tsunami hazard related to strike-slip faults, because they consist of mostly horizontal movement and relative modest vertical motion. However, ground shaking and modest uplift produced by strike slip earthquakes can generate submarine and coastal ground failure capable of generating catastrophic tsunamis. Historical documents revealed that on 27 August 1810 an earthquake affected the Loreto town and the surrounding region, along 200 km the coast of Baja California, Mexico, and damage was considerable due to strong ground motions. However, the 1810 Loreto earthquake unlike other earthquakes of the 19th and 20th centuries, produced an extensive tsunami flooding on the eastern coast of Baja California, from Loreto to La Paz. We discuss here the historical account of this event and analyse the source of the related tsunami. Based on the historical record and tectonic setting, we infer that this earthquake was produced along a transform fault, right-lateral strike slip fault, Farallon fault, on the Baja California Gulf. However, the associated tsunami was disproportionally large if compared with the earthquake intensity (IX) and approximate magnitude (7.4 Mw), fault style and the relatively tsunami late arrival, i.e. an hour after the earthquake, suggesting that a submarine landslide, triggered by this earthquake, was the suspect source for the Loreto tsunami. Historical data and a numerical model of the Loreto 1810 tsunami aid to elucidate the source, using both the 1810 earthquake and a submarine landslide, and confirm that a submarine landslide is most likely the tsunami triggering mechanism that followed the 1810 earthquake.

Presenting Author: María-Teresa Ramírez-Herrera

Authors