Symptomatic Discretization of Small Earthquake Clusters Reveals Seismic Coupling To 2017 Bodrum Earthquake (Mw 6.6) in the Gulf of Gokova (Sw Corner of Turkey): Viscous-Compliant Seismogenesis Over Back-Arc Setting

Abstract

In this study, the small relocated "same and/or similar size events" repeated in each observed cluster are deduced from temporal and spatial statistics of microseismicity. Microseismicity not exceeding Mw 5.0 that occurred in the years from 2010 to 2014 and were recorded by the network of the Turkish General Directorate of Disaster Affairs were investigated. In the Gulf of Gokova (SW corner of Turkey), the November 26, 2012 Bozburun mainshock (Mw 4.8) was evaluated with its small events, together with its accompanying aftershock sequences that occurred in three discrete areas (Bozburun, Ula, Bodrum) of the gulf: the May 16, 2013 Ula aftershock (Mw 4.6), the March 25, 2014 Bozburun aftershock (Mw 4.0), and the May 1, 2014 Bodrum aftershock (Mw 4.0). Statistical analysis was accomplished by subdividing temporal distribution of microseismicity and resorting to a number of temporal clusters that allowed the mainshock-aftershock sequence to be placed into subgroups, and thus resulted in five clusters of various sizes linked to spatial clusters. The successive occurrence and clustering of small events into distinct discrete domains in time and space allowed reliable constraints on the stress state of the study area and suggested an interaction of the clusters. The interacting clusters offered an opportunity to evaluate the seismic coupling to 2017 Bodrum earthquake (Mw 6.6) in the study area. Our portrayal of the clusters inferred from small relocated events provide an important contribution to Bozburun, Ula and Bodrum: (1) a symptomatic discretization that is "peaked-like statistical behaviors" of clusters of small relocated events through time and space is an anomalously conspicuous feature, (2) this feature proposes a process of the inevitable interaction and triggering of the discrete clusters, indicating transient acceleration of aseismic slip on surrounding, uncoupled sections of the study area, and (3) this process reveals an evidence of the viscous-compliant seismicity as a principal objective of the cluster interaction, and hence a matter of seismic coupling scenario of the clusters to 2017 Bodrum earthquake (Mw 6.6) in the study area. These conclusions highlight the importance of the seismic-aseismic slip partitioning, arresting and balancing in the co-seismic source regions of the seismically active extensional grabens in driving the large earthquakes near the future and the viscous-compliant seismogenesis over back-arc setting of the Gulf of Gokova that provides an opportunity to understand the seismic coupling processes and the current stress state of the study area. This study implicates for the extensional back-arc graben basins in the Aegean region and WSW-Turkey that require a knowledge of the linkage between upper mantle flow processes and shallow, thin crustal dynamics in the region.