Characterization of Fault-slip Taking Place in a Fractured Fault Damage Zone

In this study, we present structural, fracture orientation and fracture density (FD) data in order toquantify the deformation pattern of a damage zone that form around the slip plane of a large scalethrust fault which is located on the Ionian zone (External Hellenides) in northwestern Greece. Structuralanalysis showed at least two major deformation stages as indicated by the presence of refolding,backthrusting and break-back faulting. The fracture orientation analysis revealed three mainfracture systems, a dominant conjugate fracture system which is perpendicular to the transport direction(NW-to NNW trending sets), a conjugate fracture system trending parallel to the transport direction(ENE-trending conjugate sets) and a third diagonal conjugate fracture system (WNW andNNE trending sets). Resulting fracture density-distance diagrams display a decrease of total fracturedensity away from the studied fault, which is largely heterogeneous and irregular on both footwalland hanging wall. The conjugate fracture system trending perpendicular to the transport directionhas the dominant contribution to the accumulation of total fracture density. Based on theseresults we suggest that the observed heterogeneous and irregular distribution of fracture densityfashioned during the second deformation stage and is attributed to the formation of backthrusts andbreak-back thrust faults.

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Chapter 3. Fault-Zone Trapped Waves: High-Resolution Characterization of the Damage Zone of the Parkfield San Andreas Fault at Depth

Imaging, Modeling and Assimilation in Seismology ◽

10.1515/9783110259032.107 ◽

2012 ◽

Author(s):

Yong-Gang Li ◽

Peter E. Malin ◽

Elizabeth S. Cochran

Keyword(s):

High Resolution ◽

Fault Zone ◽

San Andreas Fault ◽

Damage Zone ◽

Trapped Waves ◽

San Andreas

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Controls on fault damage zone width, structure, and symmetry in the Bandelier Tuff, New Mexico

Journal of Structural Geology ◽

10.1016/j.jsg.2010.05.005 ◽

2010 ◽

Vol 32 (6) ◽

pp. 766-780 ◽

Cited By ~ 27

Author(s):

Paul R. Riley ◽

Laurel B. Goodwin ◽

Claudia J. Lewis

Keyword(s):

New Mexico ◽

Damage Zone ◽

Zone Width ◽

Bandelier Tuff ◽

Fault Damage Zone

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Nanoscale textural and chemical evolution of silica fault mirrors in the Wasatch fault damage zone, Utah, USA

Geochemistry Geophysics Geosystems ◽

10.1029/2020gc009368 ◽

2021 ◽

Author(s):

L.M. Houser ◽

A.K. Ault ◽

D.L. Newell ◽

J.P. Evans ◽

F‐A. Shen ◽

...

Keyword(s):

Chemical Evolution ◽

Damage Zone ◽

Fault Damage Zone ◽

Wasatch Fault

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Signature of transition to supershear rupture speed in the coseismic off-fault damage zone

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2021.0364 ◽

2021 ◽

Vol 477 (2255) ◽

Author(s):

Jorge Jara ◽

Lucile Bruhat ◽

Marion Y. Thomas ◽

Solène L. Antoine ◽

Kurama Okubo ◽

...

Keyword(s):

High Resolution ◽

Fracture Mechanics ◽

Shear Wave Velocity ◽

Observational Studies ◽

Numerical Models ◽

Damage Zone ◽

Precise Location ◽

Earthquake Ruptures ◽

Fault Damage Zone ◽

Rupture Speed

Most earthquake ruptures propagate at speeds below the shear wave velocity within the crust, but in some rare cases, ruptures reach supershear speeds. The physics underlying the transition of natural subshear earthquakes to supershear ones is currently not fully understood. Most observational studies of supershear earthquakes have focused on determining which fault segments sustain fully grown supershear ruptures. Experimentally cross-validated numerical models have identified some of the key ingredients required to trigger a transition to supershear speed. However, the conditions for such a transition in nature are still unclear, including the precise location of this transition. In this work, we provide theoretical and numerical insights to identify the precise location of such a transition in nature. We use fracture mechanics arguments with multiple numerical models to identify the signature of supershear transition in coseismic off-fault damage. We then cross-validate this signature with high-resolution observations of fault zone width and early aftershock distributions. We confirm that the location of the transition from subshear to supershear speed is characterized by a decrease in the width of the coseismic off-fault damage zone. We thus help refine the precise location of such a transition for natural supershear earthquakes.

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