← Back to Sessions

Seismic Magnitude Clustering Is Prevalent in Field and Laboratory Catalogs but Absent in Synthetic Catalogs

Description: 

Clustering of earthquake magnitudes is still actively debated, compared to well-established spatial and temporal clustering. Magnitude clustering is not currently implemented in earthquake forecasting but would be important if larger magnitude events are more likely to be followed by similar sized events. Investigating many laboratory and field catalogs, we observed magnitude clustering at a wide range of spatial scales (mm to 1000 km). Filters based on magnitude of completeness and interevent times were applied to address previous study concerns of network detection limitations and short-term aftershock incompleteness. This phenomenon was still observed after various filters were applied, demonstrating that magnitude clustering is not an artifact but a widespread phenomenon. Field results demonstrate it is universal across fault types and tectonic/induced settings, while laboratory results are unaffected by loading protocol or rock types and show temporal stability. The absence of clustering can be imposed by a global tensile stress environment in the lab, although clustering still occurs when isolating to triggered event pairs or spatial patches where shear stress dominates. Restricting the analysis to triggering-triggered pairs creates the most significant magnitude clustering patterns, far exceeding that of solely spatial or temporal clustered events. Both the lab and field analyses found magnitude clustering is more prominent at short time and distance scales, and we seek to characterize the decay in clustering over time and distance to help provide clues about the governing physical process. Synthetic catalog modeling using both ETAS and Gutenberg-Richter probability density methods indicates >20% repeating magnitudes would be necessary to explain some cases, implying it can help to narrow physical mechanisms for seismogenesis.

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

Type: Oral

Date: 4/20/2023

Presentation Time: 05:30 PM (local time)

Presenting Author: Derreck J. Gossett

Student Presenter: Yes

Invited Presentation: 

Authors