Rupture Initiation of Small Earthquakes in the Corinth Rift, Greece

Date: 4/25/2019

Time: 06:00 PM

Room: Fifth Avenue

During the last decades, recent studies evidenced differences in rupture initiation between small and large earthquakes, bringing new perspectives to understand the earthquake nucleation and helping to develop early-warning systems. Whether the final event magnitude can be estimated while the rupture is still ongoing, stays an open question and opposite points of view have been proposed regarding the deterministic nature of the rupture process.

Most of the previous studies focused on large earthquakes for their interest in risk mitigation actions. We peculiarly investigate the behavior of small ruptures, taking advantage of the dense and rich database of the Corinth Rift Laboratory in Greece. Following the approach proposed by Colombelli et al. (2014), we looked at the time evolution of the initial P-wave peak amplitude. We analyze earthquakes of magnitude M<5 with the aim of understanding the feasibility of this approach and of comparing the results with larger magnitudes. For the small events (1<M<4), we highlight a positive scaling between the averaged P-wave peak velocity at the early stage of the rupture and the final earthquake size, opposed to the tendency found for larger Japanese earthquakes. In the Corinth Rift, we suggest that the higher the slip rate is in average, the larger the earthquake is. This interpretation can be illustrated by considering shortly distant asperities: if the slip rate is low, only one asperity breaks resulting in low-magnitude event, whereas if the slip rate is high, enough energy is released to propagate the rupture to several connected asperities.

Further analyses are needed to validate the results, especially by investigating several factors (time sampling, attenuation, etc.) to fully understand the observed behaviors. Moreover, given the availability of seismic multiplets in the Corinth Rift, which are associated to different external forcings (pore pressure, aseismic slip), it would be interesting to investigate a possible distinction in rupture initiation behavior as a function of specific forcing sources.

Presenting Author: Clara Duverger

Authors