Back to Search Start Over

Probing the Southern Cascadia Plate Interface With the Dense Amphibious Cascadia Initiative Seismic Array.

Authors :
Alongi, T.
Schwartz, S. Y.
Shaddox, H. R.
Small, D. T.
Source :
Journal of Geophysical Research. Solid Earth. Jul2021, Vol. 126 Issue 7, p1-13. 13p.
Publication Year :
2021

Abstract

Fault coupling is vital in determining the amount of strain that is accumulated along faults. The magnitude and location of stored elastic strain energy in highly coupled regions has important implications for understanding the full range of slip behavior at plate boundary faults, as well as earthquake and tsunami hazards. We use the temporary dense amphibious array of seismometers offered by the Cascadia Initiative to create a high‐resolution catalog of events to examine the spatio‐temporal behavior of earthquakes near the plate interface. The data show that in southern Cascadia the plate interface updip of the geodetically locked region is nearly devoid of seismicity, therefore likely highly coupled and accumulating strain. The catalog reveals events that are clustered at the downdip edge of the highly coupled megathrust that correlate in time with nearby strain transient observations. Template matching of events in the cluster using permanent stations of the Northern California Seismic Network over a 10‐year period between 2010 and 2020 indicates that this cluster is unique in space and time. Its activity only during the strain transient provides support for the utility of seismic observations in the identification of strain transients. Plain Language Summary: Great megathrust earthquakes have occurred in the Cascadia Subduction Zone. The most recent occurred in 1700, and it is expected that another will happen in the next few hundred years. Although the megathrust has hosted great earthquakes, few small interplate events have been identified along this plate boundary. Instead, a portion of the convergence between the tectonic plates is released in both periodic slow slip events and (quasi) continuous fault creep. It is essential to understand the full range of plate boundary behavior to assess the hazard risk for great earthquakes. To further this understanding, we gather data using a densely spaced temporary array of seismometers deployed in southern Cascadia in 2014–2015 to increase detection as well as determine precise earthquake locations. We identify events that are on or very near the plate boundary fault. There is some clustering of earthquakes near the plate boundary, but we find an absence of earthquakes along the shallowest segment, that indicate that the fault is likely locked. When compared to other geophysical observations in the area, it appears that the cluster of earthquakes near the plate boundary is sensitive to strain transients, demonstrating the utility of seismic observations in investigating these phenomena. Key Points: Catalog creation of 1,452 events in southern CascadiaLack of shallow offshore plate interface seismicity suggests locally high couplingTemplate matching of plate interface events reveals a cluster of seismicity sensitive to long‐term plate interface strain transients [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
21699313
Volume :
126
Issue :
7
Database :
Academic Search Index
Journal :
Journal of Geophysical Research. Solid Earth
Publication Type :
Academic Journal
Accession number :
151650769
Full Text :
https://doi.org/10.1029/2021JB022180