New Insight Into the Frequency-Dependent Radiation of Subduction-Zone Earthquakes From Dynamic Simulations of Megathrust Ruptures
Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems II
Type: Oral
Date: 4/20/2021
Presentation Time: 09:45 AM Pacific
Description:
The recent observation that the radiation of megathrust earthquakes exhibits frequency-depth dependence seems ubiquitous: most the low frequency (LF) seismic radiation is emitted at shallow depths while the high frequency (HF) seismic radiation is emitted at greater depths. The explanation most evoked is a systematic depth variation in stress or frictional properties along the plate interface. In this study, we build dynamic rupture models for megathrust earthquakes in realistic 2D elastic structure. We use P-wave velocity Vp of the Tohoku area from Miura et al. (2005) and also explore a large parameter space for on-fault frictional and pre-stress properties.
All 28 modeled ruptures present the common patterns: the slip motions near the trench are those of crack-like ruptures with smooth slip rate functions, while the slip motions on the downdip are those of pulse-like ruptures with sharp slip rate functions. We further quantify the depth-frequency relation along slab by (1) calculating the power ratio of HF and LF slip acceleration and (2) fitting a Brune-type spectral model for the spectral falloff rate. Both quantifications show the same patterns for those dynamic models: the HF-LF power ratio increases and the falloff rate decreases from the updip to downdip to confirm that HF radiation is more efficient downdip and LF radiation is more efficient updip. Our findings suggest that i) the effect of the Earth free surface on dynamic rupture is the dominant factor that explains the frequency-depth variation, ii) the low-velocity zone of a hydrated down-going slab aggravates the contrast in radiation, and that iii) realistically high Vp/Vs in the frontal prism yield greater potential for tsunamigenesis.
Presenting Author: Jiuxun Yin
Student Presenter: Yes
Authors
Jiuxun Yin Presenting Author Corresponding Author jiuxun_yin@g.harvard.edu Harvard University |
Marine Denolle mdenolle@uw.edu University of Washington |
|
|
|
|
|
|
|
New Insight Into the Frequency-Dependent Radiation of Subduction-Zone Earthquakes From Dynamic Simulations of Megathrust Ruptures
Category
Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems