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Session: Earthquake Source Parameters: Theory, Observations and Interpretations

Type: Oral

Date: 4/25/2019

Time: 11:15 AM

Room: Cascade I

Relative Moment Tensors Revisited

We introduce new relative moment tensor (MT) inversion methods for clusters of nearby earthquakes. P-wave relative amplitudes are obtained from the best-fit ratio of aligned waveforms, with no need to pick pulse amplitudes. For S-waves we produce constraints on MT elements involving three events, where one event is described as a linear combination of the other two. This approach does not require modal decomposition into SV and SH. Singular-value decomposition on aligned waveforms is presented as an efficient means to derive the relative MT constraints. Non-linear methods are introduced to efficiently find best-fit tensile earthquake and double-couple solutions for relative MT systems. Using synthetic data, we demonstrate the effectiveness of the P and S constraints both individually and combined. We then apply the method to a set of 16 intermediate-depth earthquakes from southern Alaska, in the subducted Yakutat terrane, and compare unconstrained, deviatoric, tensile earthquake, and double-couple MT solutions. We observe earthquakes with antiparallel slip occurring 5 km apart, indicating that complex deformation in this region of the Yakutat. The relative MT method is also applied to two larger clusters in the continental crust of northern Washington, both containing several hundred events.

Presenting Author: Alexandre P. Plourde

Additional Authors