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Linking Fault Roughness at Seismogenic Depths to Earthquake Behavior

Description: 

Fault geometry affects the initiation, propagation, and cessation of earthquake rupture, as well as, potentially, the statistical behavior of earthquake sequences. We analyze 18,250 earthquakes comprising the 2016-2019 Cahuilla, California swarm and, for the first time, use high-resolution earthquake locations to map, in detail, the roughness across an active fault surface at depth. We find that the fault is 50% rougher in the slip-perpendicular direction than parallel to slip. Roughness estimates are spatially variable, and fluctuate by a factor of 8 over length scales of 1 km. We observe that the largest earthquake (M4.4) occurs where there is significant fault complexity and the highest measured roughness. We also find that b-values are weakly positively correlated with fault roughness. Following the largest earthquake, we observe a distinct population of earthquakes with comparatively low b-values occurring in an area of high roughness values within the rupture area of the M4.4 earthquake. Finally, we measure roughness at multiple scales and find that the fault is self-affine with a Hurst exponent of 0.52, consistent with a Brownian surface.

Session: Deciphering Earthquake Clustering for the Better Understanding of Crustal Deformation Mechanisms

Type: Oral

Date: 4/20/2023

Presentation Time: 04:45 PM (local time)

Presenting Author: Morgan Page

Student Presenter: No

Invited Presentation: 

Authors