Quimper Geological Society

The Lecture:  An Exhumed Ancient Cascadia Megathrust Fault in the Olympic Mountains

On October 5, 2024 the Quimper Geological Society will host a lecture by Harold Tobin, professor of Seismology and Geohazards at the University of Washington and Director of the Pacific Northwest Seismic Network. Harold’s research employs field mapping and geophysical techniques to investigate processes that operate in fault zones, particularly those associated with subduction zones. One of his study areas is the Olympic Mountains, where recently he and his graduate students mapped rocks in a remote area west of Mount Olympus that were covered by ice when geologists last visited the area over 50 years ago. They found intensely deformed rocks that represent a fossil megathrust fault, the type of fault responsible for great Cascadia earthquakes. Harold will discuss how integrating data from this ancient fault with seismic imaging of present-day seismic zones allow him to better understand how and why these megathrust faults slip and generate earthquakes.

This IN-PERSON ONLY lecture will start at 4 PM on Saturday, October 5, 2024. This is free and open to the public. (Donations gratefully welcome at the door.) This lecture will be recorded and posted shortly after the presentation, as are all our events since 2020.

About the Speaker:

Professor Harold Tobin holds the Paros Endowed Chair in Seismology and Geohazards at the Department of Earth and Space Sciences at the University of Washington. He also serves as the Director of the Pacific Northwest Seismic Network and Washington’s State Seismologist. Despite that title, his scientific roots are in subduction zone geology and the structure of plate boundary fault zones. With a B.S. in geology and geophysics from Yale University and a PhD from University of California, Santa Cruz, Harold has held faculty positions at New Mexico Tech and the University of Wisconsin-Madison prior to moving to Seattle in 2018. His first taste of subduction geology was as an undergraduate field assistant in the Olympic Mountains in 1987, and after 30 years of offshore and onshore research in Japan, Alaska, New Zealand, Costa Rica, and California, he has come full circle to explore the core rocks of the Olympic mountains.