Different phases of the earthquake cycle captured by seismicity along the North Anatolian Fault

Abstract

The North Anatolian Fault has accommodated three major earthquakes during the last 15 years. Although the fault zone has substantially failed during the last century, it did not completely fail in NW Turkey and therefore left several segments at different physical stages. In this study, the seismicity rate is used as a proxy to locate the brittle fault sections with high/low strain accumulation. The results show that the 1999 M7.4 İzmit and the 2014 M6.9 Aegean earthquakes were preceded by almost a decade‐long period of enhanced microearthquake activity representing a brittle process preparing the failure. This interpretation is supported by observed lateral migration of microearthquakes toward the main shock hypocenter within a time scale of roughly a decade. The Sea of Marmara segments of the North Anatolian Fault show a rather temporally uniform seismicity trend leading to the hypothesis that those segments are still not in the preparation stage for a large earthquake. The results also show that the duration of aftershock activity is not controlled only by the size of main shocks.

Fault slip source models for the 2014Mw6.9 Samothraki‐Gökçeada earthquake (North Aegean Trough) combining geodetic and seismological observations

“…The 2014 rupture was preceded and possibly facilitated by a ~10 year long interval of increased microearthquake activity which perhaps prepared the failure [ Bulut , ] and permitted the release nearly of the whole of the cumulated elastic strain during the main shock, by one or preferably two nearly planar strike‐slip ruptures and supershear fracture according to Evangelidis []. Interestingly, increased microseismic activity preceding a supershear rupture was also observed during the Izmit 1999 earthquake, the last event along the NAFZ [ Bouchon et al ., ; Bulut , ].…”

A Multiparametric Approach to Study the Preparation Phase of the 2019 M7.1 Ridgecrest (California, United States) Earthquake

“…Nevertheless, it is rather difficult to think that a so large energetic phenomenon such as a strong earthquake cannot provide any sign of its preparation (e.g., Sobolev et al, 2002;Bulut 2015). With this work, we want to give a fundamental contribution to the study of the preparation phase of earthquakes, considering the case study of the 2019 Ridgecrest seismic sequence.…”

Seismic rate variations prior to the 2010 Maule, Chile MW 8.8 giant megathrust earthquake

“…In practice, a large number of parameters can influence the regularity of the cycle, as a number of space and time scales are involved and the first approximation of elastic surrounding materials (crusts, plates) is somewhat simplistic. Only a few examples of observed seismic cycles are documented 15,16 , where the interseismic period corresponds to low seismic activity or aseismic faulting followed (or not) by brittle seismic ruptures preceding the main event. These foreshocks, corresponding to bursts of seismic activity occurring in a short time before a large earthquake and close to its rupture zone, have been frequently observed in various zones and contexts (intraplate/interplate [17][18][19] , subduction earthquakes 3,20 ), but their mechanical connection with the large earthquakes that follow are still unclear [21][22][23] .…”