Our IGPP alumnus, Prof. Diego Melgar from the University of Oregon, is presenting his work in our upcoming GP Seminar. The seminar will be held in the Munk conference room on coming Wednesday, May 7th, at 3:00 pm.
Title:
Paleoseismology and Geophysical Models of the Great 1700 Cascadia Earthquake
Abstract:
The 1700 C.E. Cascadia earthquake is one of the most well-documented prehistoric megathrust events, evidenced by coastal subsidence, tsunami deposits, offshore turbidites, and historical records of an "orphan" tsunami in Japan. While traditionally interpreted as a single full-margin Mw ~9 earthquake, advances in rupture and tsunami modeling suggest a broader spectrum of possibilities. Using thousands of synthetic rupture scenarios, including both full-margin events and multi-event sequences, we compare modeled deformation and inundation against paleoseismic constraints from 26 coastal subsidence sites, seven mapped tsunami deposits, and Japanese tsunami heights. Results favor a full-margin rupture with up to 30 m of slip and shallow geodetic coupling. However, certain rupture sequences composed of three to five Mw 8–8.7 events also replicate the observations, indicating that segmented rupture remains a viable explanation. These findings highlight the power of combining paleoseismology with geophysical modeling to explore rupture complexity and improve Cascadia hazard assessments.