Systematization of active faults for the assessment of the seismic hazard |
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Authors: | O V Lunina A S Gladkov A A Gladkov |
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Institution: | 1.Institute of the Earth’s Crust, Siberian Branch,Russian Academy of Sciences,Irkutsk,Russia |
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Abstract: | A systematization of active faults has been developed based on the progress of scientists from the leading countries in the
world in the study of seismotectonics and seismic hazard problems. It is underlain by the concept of the fault-block structure
of the geological-geophysical environment governed by the interaction of differently oriented active faults, which are divided
into two groups—seismogenic and nonseismogenic faults. In seismogenic fault zones, the tectonic stress accumulated is relieved
by means of strong earthquakes. Nonseismogenic fault zones are characterized by creep displacement or short-term, oscillatory,
and reciprocal movements, which are referred to local superintense deformations of the Earth’s crust (according to the terminology
used by Yu.O. Kuz’min). For a situation when a strong earthquake happens, a subgroup of seismodistributing faults has been
identified that surround the seismic source and affect the distribution of the seismic waves and, as a consequence, the pattern
of the propagation of the coseismic deformations in the fault-block environment. Seismodistributing faults are divided into
transit and sealing faults. Along transit faults, secondary coseismic effects (landfalls, landslides, ground fractures, liquefaction,
etc) are intensified during earthquakes. In the case of sealing faults, enhancement of the coseismic effects can be observed
on the disjunctive limb nearest to the epicenter, whereas, on the opposite limb, the intensity of such effects appreciably
decreases. Seismogenic faults or their systems are associated with zones of earthquake source origination (ESO), which include
concentrated seismicity regions. In such zones, each earthquake source is related to the evolution of a fault system. ESO
zones also contain individual seismogenic sources being focuses of strong earthquakes with M of ≥5.5 in the form of ruptures, which can be graphically represented in 2D or 3D as a surface projection of the source.
Depending on the type of data based on which they are identified, individual seismogenic sources are divided into geological-geophysical
and macroseismic sources. The systematization presented is the theoretical basis for and the concept of the relational database
that is being developed by the authors as an information system for the generation of seismotectonic GIS projects required
for the subsequent analysis of the seismic hazard and the assessment of the probability of the origination of macroseismic
earthquake effects in a predetermined location. |
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