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An Updated Version of the New Empirical Source-Scaling Laws for Crustal Earthquakes Incorporating Fault Dip and Seismogenic-Thickness Effects

Description: 

New global source-scaling relations for the aspect ratio and rupture area for crustal earthquakes, including the width-limited effect and a possible free-surface effect, are derived using a global data set of finite-fault rupture models. In contrast to the commonly used scaling relations between moment magnitude (M), fault length (L), width (W), and area, we built self-consistent scaling relations by relating M to the aspect ratio (L/W) and to the fault area to model the change in the aspect ratio once the rupture width reaches the down-dip width limit of the fault. The width-limited effect for large-magnitude earthquakes depends on the fault dip and a regional term for the seismogenic thickness. The magnitude scaling of the aspect ratio includes a break in the magnitude scaling that is dip-angle-dependent. This dip-angle-dependent magnitude scaling in the magnitude-area relation is thereby modeled by a trilinear relation incorporating a dip-related transition range. The effect of the free surface was observed using a normalized depth term and parameterizing the source by the depth of the top of the fault rupture; it is more apparent in the area scaling relation. The scaling differences are related to the fault geometry, not the rake angle, as commonly assumed. Finally, the corresponding L and W scaling relations obtained by converting the area and aspect-ratio models to L and W models showed good agreement with the previous regional scaling laws on average but provided better fault-specific application due to the inclusion of fault-specific dip angles and seismogenic thicknesses.

Session: The 2023 USGS National Seismic Hazard Model and Beyond - III

Type: Oral

Date: 5/1/2024

Presentation Time: 03:00 PM (local time)

Presenting Author: Jyun-Yan

Student Presenter: No

Invited Presentation: 

Authors