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Multiscale Amphibious Experiments at Subduction Zones: Recent Advancements and Future Directions

Session: Amphibious Seismic Studies of Plate Boundary Structure and Processes

Type: Oral

Date: 4/20/2021

Presentation Time: 09:45 AM Pacific

Description: 

The amphibious setting of subduction zones has traditionally limited seismic imaging of these regions, particularly within coastal forearcs and oceanic island arc environments that require a mixture of onshore and offshore seismic instrumentation. This is additionally complicated by the multiscale nature of seismic imaging targets at subduction zones that are relevant for understanding earthquake and volcanic processes. Recent amphibious seismic experiments offer an unprecedented view of subduction zones, allowing continuous seismic imaging from the incoming oceanic plate, across the forearc, and into the arc and backarc regions. Here we highlight both active and natural-source amphibious seismic imaging results from the Cascadia subduction zone. Ship-to-shore airgun shots and offshore receiver function imaging reveal a heterogenous plate interface with variations in velocity and reflectivity on the scale of tens of kilometers. In particular, regions of low velocities along the plate interface, which may be related to variations in plate locking, are observed. Along the subduction margin, extending from northern California to northern Washington, surface wave imaging yields new images of the oceanic Juan de Fuca plate and forearc, and improves phase velocity maps onshore near the coastline relative to prior results using only land-based data. Obtaining these results, which rely on data from broadband ocean-bottom seismometers deployed in shallow water on the continental shelf, requires careful analysis and preprocessing to remove oceanographic noise. Such challenges broadly impact subduction studies, as many geographic regions share similar, technical challenges. Lastly, we discuss future directions for amphibious targets and experiment design, highlighting recent onshore results from the Aleutian island arc and current limitations due to an absence of offshore instrumentation.

Presenting Author: Helen A. Janiszewski

Student Presenter: No

Authors