pure and applied geophysics

, Volume 160, Issue 5–6, pp 1051–1066 | Cite as

Triggering of Seismicity by Pore-pressure Perturbations: Permeability-related Signatures of the Phenomenon

  • S. A. Shapiro
  • R. Patzig
  • E. Rothert
  • J. Rindschwentner

Abstract

— We consider various cases of seismicity, induced by artificial fluid injections in boreholes. Like many other authors, we support the hypothesis that to a large extent the triggering of this seismicity is caused by a diffusive process of the pore pressure relaxation in porous (or fractured), saturated rocks. We show that if this hypothesis is correct, then the spatio-temporal distributions of the seismic events must have several specific features related to the effective permeability of the rock. As a rule the fluid injection-induced seismicity obeys such features. These features can be indications of the diffusive and even hydraulic nature of the seismicity triggering process.¶From this point of view we analyze the spatio-temporal distribution of the late aftershocks of the Antofagasta (northern Chile) 1995 earthquake. These aftershocks were concentrated in a plane, an approximately 3 km-thick spatial zone. This thin seismogenic layer is a part of the South American subduction zone. The time-distance distribution of the aftershocks along this layer indicates that they could be triggered by a diffusion-like process. Possibly, such a process is the relaxation of the pressure perturbation caused in the pore fluid by the main Antofagasta event. We estimated the permeability required to explain the spatio-temporal distribution of the aftershocks by such a triggering mechanism. The obtained value, 60 mD, is very large. However, it is realistic for a long-time existing and large-scale fault zone.

Key words: Diffusivity, permeability, aftershocks, seismicity, subduction. 

Copyright information

© Birkhäuser Verlag, Basel, 2003

Authors and Affiliations

  • S. A. Shapiro
    • 1
  • R. Patzig
    • 1
  • E. Rothert
    • 1
  • J. Rindschwentner
    • 1
  1. 1.Freie Universität Berlin, Fachrichtung Geophysik, Malteserstr. 74-100, 12249 Berlin, Germany. E-mail: shapiro@geophysik.fu-berlin.de, rip@geophysik.fu-berlin.de, rothert@geophysik.fu-berlin.de, janr@geophysik.fu-berlin.deDE

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