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Revised history of the interplate earthquakes along the Sagami Trough

Event Type: 
Seminar
Event Date: 
12 October 2018 - 4:00pm to 5:00pm
Venue: 
ASE 3-D Visualization Lab (N2-B1c-16c)
Speaker: 
Junki Komori
About the speaker: 

Junki is a visiting Ph.D. student from the University of Tokyo, Japan. He received B.Sc. (2016) in Earth and Planetary Environmental Science from the University of Tokyo. He has published one academic article related to the part of today’s talk at EPSL as the first author.

About the event: 

As evidence of the recurrence of the past M8 class subduction earthquakes, the marine terraces along the southernmost coast of the Boso Peninsula, central Japan, called Numa terraces, have been investigated for a long time. For the future hazard assessment around there, it is necessary to understand the formation history of them.

We reexamined it by updated geomorphological and geological surveys. First, we conducted a landform investigation using digital elevation model (DEM) to identify the paleo-shorelines whose elevation corresponds to the accumulated vertical deformation since their emergence. Second, the formation ages of the Numa terraces were re-estimated by dating survey. A highly reliable estimation was realized due to a dense drilling survey in this study.

The result of the dating showed that the formation intervals of the Numa terraces greatly differ with each other, unlike the previous interpretation. On the other hand, the result of the DEM analysis showed that the Numa terraces’ relative heights have almost same distribution. These two results are inconsistent with each other considering the classical deformation model of earthquake recurrence.