Publication Date:
2017-04-04
Description:
We model a fault cross-cutting the brittle upper crust and the ductile lower crust. In the brittle layer the fault is assumed to have stick-slip behaviour, whereas the lower ductile crust is inferred to deform in a steady-state shear. Therefore, the brittle-ductile transition (BDT) separates two layers with different strain rate and structural style. This contrasting behaviour determines a stress gradient at the BDT that is eventually dissipated during the earthquake. During the interseismic period, along a normal fault there should form a dilated hinge at and above the BDT. Conversely, an over-compressed volume should rather develop above a thrust plane at the BDT. On a normal fault the earthquake is associated with the coseismic closure of the dilated fractures generated in the stretched hangingwall during the interseismic period. In addition to the shear stress overcoming the friction of the fault, the brittle fault moves when the weight of the hangingwall exceeds the strength of the dilated band above the BDT. On a thrust fault, the seismic event is instead associated with the sudden dilation of the previously over-compressed volume in the hangingwall above the BDT, a mechanism requiring much more energy because it acts against gravity. In both casess, the deeper the BDT, the larger the involved volume, and the bigger the related magnitude.
We tested two scenarios with two examples from L’Aquila 2009 (Italy) and Chi-Chi 1999 (Taiwan) events. GPS data, energy dissipation and strain rate analysis support these contrasting evolutions. Our model also predicts, consistently with data, that the interseismic strain rate is lower along the fault segment more prone to seismic activation.
Description:
This research has benefited from funding provided by the Italian Presidenza del Consiglio dei Ministri - Dipartimento della Protezione Civile (DPC) within the INGV-DPC 2007-2009 agreement (project S1), Sapienza University, CNR, Eurocores, TopoEurope.
Description:
In press
Description:
3.1. Fisica dei terremoti
Description:
3.2. Tettonica attiva
Description:
4.3. TTC - Scenari di pericolosità vulcanica
Description:
JCR Journal
Description:
open
Keywords:
brittle-ductile transition
;
thrust
;
normal fault
;
dilatancy
;
seismic cycle
;
L’Aquila Italy
;
Chi-Chi Taiwan
;
earthquake
;
04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes
;
04. Solid Earth::04.01. Earth Interior::04.01.05. Rheology
;
04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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