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The 2020 Perachora peninsula earthquake sequence (Εast Corinth Rift, Greece): spatiotemporal evolution and implications for the triggering mechanism

Michas Georgios, Kapetanidis Vasilis, Spingos Ioannis, Kaviris George, Vallianatos Filippos

Acta Geophysica

2022

Vol. 70, no 6

2581--2601

In this work, we study the January 1, 2020 – June 8, 2021, earthquake activity in the East Corinth Rift (central Greece), one of the most seismically active areas in Europe. During this period an intense earthquake sequence occurred in the Perachora peninsula, presenting the characteristics of swarm activity. We present a relocated earthquake catalogue for the area, derived with the double-difference algorithm, and study the spatiotemporal evolution of the 2020 Perachora peninsula earthquake sequence and the possible triggering mechanisms. The Perachora sequence presents distinct characteristics of earthquake migration along a N 103º E direction, as indicated by the Principal Component Analysis, from the east toward northwest and then west, with successive deepening of the events. This migration pattern is compatible with a pore-fluid pressure triggering front of hydraulic diffusivity of D =2.8 m2 /s and an average velocity of 0.22 km/day. In addition, the sequence presents sub-diffusion, with a diffusion exponent of 0.89±0.06. The analysis, overall, indicates that the Perachora sequence was triggered at shallow depths by fluid overpressures, possibly generated by down-going fuxes of meteoric fluids, and then driven by pore-fluid pressure diffusion along the activated structures.

Subdiffusion of volcanic earthquakes

Abe S., Suzuki N.

Acta Geophysica

2017

Vol. 65, no. 3

481--489

A comparative study is performed on volcanic seismicities at Icelandic volcano, Eyjafjallajökull, and Mt. Etna in Sicily from the viewpoint of complex systems science, and the discovery of remarkable similarities between them is reported. In these seismicities as point processes, the jump probability distributions of earthquakes (i.e., distributions of the distance between the hypocenters of two successive events) are found to obey the exponential law, whereas the waiting-time distributions (i.e., distributions of inter-occurrence time of two successive events) follow the power law. A careful analysis is made about the finite size effects on the waiting-time distributions, and the previously reported results for Mt. Etna (Abe and Suzuki 2015) are reinterpreted accordingly. It is shown that the growth of the seismic region in time is subdiffusive at both volcanoes. The aging phenomenon is commonly observed in the “event-time-averaged” mean-squared displacements of the hypocenters. A comment is also made on (non-)Markovianity of the processes.