09:15 〜 09:30
[J03-1-03] Slow Slip Events in Cascadia: Observation and Hazard Analysis Derived from Sentinel-1 InSAR
Slow slip events (SSEs), also known as silent earthquakes or episodic tremor and slip (ETS), are earthquakes unfolding in slow motion. Energy release over a long time causes seismic waves with such long periods that the motion is imperceptible to all but the most sensitive instruments, and with little short-period shaking. The total moment released in an SSE may be quite large, and stress transfer from the event may either increase or relax elastically stored strain. It is important to understand the nature and impact of these often regularly-repeating and predictable events, and whether they are adding to hazard potential or ameliorating it.
Here we report on our efforts to help assess the earthquake hazard along the Cascadia region of the Pacific northwest and determine, from spaceborne InSAR data, if SSE events are affecting the earthquake risk. We produce spatially dense crustal deformation observations that, when used with the existing GPS and seismic data, can localize and assess the size of slow displacements. Our goal is to measure SSE crustal displacements in Cascadia, using InSAR with finer and more comprehensive coverage than the existing GPS network, to solve for both a model of the slip at depth and the potential for a large and destructive earthquake.
The challenge of InSAR over Cascadia is that the dense forest cover leads to significant InSAR decorrelation. We use persistent scatterer (PS) point identification, interpolation of the sparse phase field, inverse solutions optimized for transient detection, and separation of the secular and transient signals, which may allow for a superior assessment of the hazard potential of a massive earthquake in the Pacific northwest. This work is, to our knowledge, the first implementation of the type of hazard analysis from crustal deformation that has been shown in Hawaii and Mexico to an environment where nearly all of the surface is hidden beneath a very thick vegetation canopy.
Here we report on our efforts to help assess the earthquake hazard along the Cascadia region of the Pacific northwest and determine, from spaceborne InSAR data, if SSE events are affecting the earthquake risk. We produce spatially dense crustal deformation observations that, when used with the existing GPS and seismic data, can localize and assess the size of slow displacements. Our goal is to measure SSE crustal displacements in Cascadia, using InSAR with finer and more comprehensive coverage than the existing GPS network, to solve for both a model of the slip at depth and the potential for a large and destructive earthquake.
The challenge of InSAR over Cascadia is that the dense forest cover leads to significant InSAR decorrelation. We use persistent scatterer (PS) point identification, interpolation of the sparse phase field, inverse solutions optimized for transient detection, and separation of the secular and transient signals, which may allow for a superior assessment of the hazard potential of a massive earthquake in the Pacific northwest. This work is, to our knowledge, the first implementation of the type of hazard analysis from crustal deformation that has been shown in Hawaii and Mexico to an environment where nearly all of the surface is hidden beneath a very thick vegetation canopy.