The role of the fault-block structure of the continental margin in the
generation of the strongest subduction earthquakes
- Irina Vladimirova,
- Yury Gabsatarov,
- Dmitry Alexeev,
- Leopold Lobkovsky
Irina Vladimirova
Moscow Institute of Physics and Technology (State University)
Corresponding Author:ir.s.vladimirova@yandex.ru
Author ProfileYury Gabsatarov
Moscow Institute of Physics and Technology (State University)
Author ProfileDmitry Alexeev
Moscow Institute of Physics and Technology (State University)
Author ProfileLeopold Lobkovsky
Moscow Institute of Physics and Technology (State University)
Author ProfileAbstract
Modern seismotectonic studies are aimed at obtaining a self-consistent
explanation of fault zone heterogeneity, the rupture process, recurrence
times and rupture mode of large earthquake sequences. In subduction
regions large earthquakes are often characterized by very long source
zones and complex long-term postseismic processes following the
coseismic release of accumulated elastic stresses. A set of mechanical
models was proposed to describe the generation of strongest earthquakes
based on the idea of the synchronous failure of several adjacent
asperities. In this study we propose a model which is based on verified
numerical schemes, which allows us to quantitatively characterize the
process of generation of strong earthquakes. The model takes into
account the fault-block structure of the continental margin and combined
the ideas of a possible synchronous destruction of several adjacent
asperities, mutual sliding along a fault plane with a variable
coefficient of friction and subsequent healing of medium defects under
high pressure conditions. The applicability of the proposed model is
shown by the example of the recent seismic history of the Kuril
subduction zone. Kuril island arc is one of the most tectonically active
regions of the world due to very high plate convergence rate.
Heterogeneities in the mechanical coupling of the interplate interface
in this region lead to the formation of the block structure of the
continental margin, which is confirmed by various geological and
seismological studies. GPS observations recorded at different stages of
seismic cycle related to the 2006--2007 Simushir earthquakes allow us to
model geodynamic processes of slow strain accumulation and its rapid
release during the earthquake and the subsequent posteseismic process.
We use parameters describing the regional tectonic structure and
rheology obtained from the inversion of geodetic data to construct a 2D
model of generation of large earthquakes in central Kurils. Analysis of
paleoseismic data on dates and rupture characteristics of previous major
earthquakes shows a good agreement between the modeled and observed
seismic cycle features. The predicted horizontal displacements of the
seismogenic block at the coseismic stage are consistent with satellite
geodetic data recorded during the 2006 Simushir earthquake. The proposed
model provides new insights into the geodynamic processes controlling
the occurrence of strong subduction earthquakes.