Abstract
Whether the stress-loading of faults to failure in earthquakes appears to be random or to an extent explainable, given constraints on fault/shear-zone interaction and the build-up and release of stress over many earthquake cycles, is a key question for seismic hazard assessment. Here we investigate earthquake recurrence for a system of 25 active normal faults arranged predominantly along strike from each other, allowing us to isolate the effects of stress-loading due to regional strain versus across- and along-strike fault interaction. We calculate stress changes over 6 centuries due to interseismic loading and 25 > Mw 5.5 earthquakes. Where only one fault exists across strike, stress-loading is dominated by the regional tectonics through slip on underlying shear zones and fault planes have spatially smooth stress with predominantly time-dependent stress increase. Conversely, where faults are stress-loaded by across-strike fault interactions, fault planes have more irregular stress patterns and interaction-influenced stress loading histories. Stress-loading to failure in earthquakes is not the same for all faults and is dependent on the geometry of the fault/shear-zone system.
Highlights
Whether the stress-loading of faults to failure in earthquakes appears to be random or to an extent explainable, given constraints on fault/shear-zone interaction and the build-up and release of stress over many earthquake cycles, is a key question for seismic hazard assessment
In this paper we examine a fault system in southern Italy where we can isolate the effects of regional tectonic loading from across strike fault interaction, because in places only a single fault accommodates all of the regional deformation, whereas elsewhere several faults exist across strike and interact to share the tectonic strain (Fig. 1)
Our study strongly supports the notion that there is a time-dependent process influenced by fault geometry, in that stress-loading to failure occurs through far-field tectonic loading and near-field interactions between faults
Summary
Whether the stress-loading of faults to failure in earthquakes appears to be random or to an extent explainable, given constraints on fault/shear-zone interaction and the build-up and release of stress over many earthquake cycles, is a key question for seismic hazard assessment. In this paper we examine a fault system in southern Italy where we can isolate the effects of regional tectonic loading from across strike fault interaction, because in places only a single fault accommodates all of the regional deformation, whereas elsewhere several faults exist across strike and interact to share the tectonic strain (Fig. 1) For this area the existence and behaviour of shear-zones is constrained by a study of the link between the topographic drive for extension and strain-rates measured over multiple m illennia[11].
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