Keyboard Model of Seismic Cycle of Great Earthquakes in Subduction Zones: Simulation Results and Further Generalization

Leopold I Lobkovsky,Dmitry A Alekseev,Yurii V Gabsatarov,Irina S Vladimirova

doi:10.3390/app11199350

Leopold I Lobkovsky, Dmitry A Alekseev + Show 2 more

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https://doi.org/10.3390/app11199350

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Journal: Applied sciences	Publication Date: Oct 8, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Moscow Institute of Physics and Technology

Abstract

Catastrophic megaearthquakes (M > 8) occurring in the subduction zones are among the most devastating hazards on the planet. In this paper we discuss the seismic cycles of the megathrust earthquakes and propose a blockwise geomechanical model explaining certain features of the stress-deformation cycle revealed in recent decades from seismological and satellite geodesy (GNSS) observations. Starting with an overview of the so-called keyboard model of the seismic cycle by L. Lobkovsky, we outline mathematical formalism describing the motion of seismogenic block system assuming viscous rheology beneath and between the neighboring elastic blocks sitting on top of the subducting slab. By summarizing the GNSS-based evidence from our previous studies concerning the transient motions associated with the 2006–2007 Simushir earthquakes, 2010 Maule earthquake, and 2011 Tohoku earthquake, we demonstrate that those data support the keyboard model and reveal specific effect of the postseismic oceanward motion. However, since the seismogenic blocks in subduction systems are mostly located offshore, the direct analysis of GNSS-measured displacements and velocities is hardly possible in terms of the original keyboard model. Hence, the generalized two-segment keyboard model is introduced, containing both frontal offshore blocks and rear onshore blocks, which allows for direct interpretation of the onshore-collected GNSS data. We present a numerical computation scheme and a series of simulated data, which exhibits the consistency with measured motions and enables estimating the seismic cycle characteristics, important for the long-term earthquake forecasting.

Highlights

Introduction published maps and institutional affilLarge-magnitude subduction-associated earthquakes with M > 8 cause the release of enormous elastic stresses accumulated over hundreds of years or even a millennium
Available geological and seismological data suggest the existence of the fault interfaces separating the offshore frontal blocks from the onshore rear ones [15,33,34], which means that the complete geomechanical model should incorporate both frontal and rear structural parts, allowing for a complex interaction between them
The two-segment keyboard-block model is represented by a series of elastic blocks forming two chains separated by fault zones extending along the subduction axis (Figure 8)

Summary

Introduction

Large-magnitude subduction-associated earthquakes with M > 8 cause the release of enormous elastic stresses accumulated over hundreds of years or even a millennium. Forecast of such shocks, leading to substantial social, economic and ecological consequences, is one of the most crucial problems in geophysics [1,2]. The most developed forecastrelated approaches include deformational monitoring [3,4,5], identification of geophysical precursors, as well as statistical analysis of the seismicity pattern [6,7,8]. Machine learning (ML) techniques and big data analysis have become a trend in recent years, and have potential to increase forecast reliability [9]. Some physical (mechanical) model is strongly needed for appropriate description of geodynamical setting during the earthquake iations

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