Title: Seismic rupture and ground accelerations induced by CO ₂ injection in the shallow crust

Abstract

We present that because of the critically stressed nature of the upper crust, the injection of large volumes of carbon dioxide (CO ₂) into shallow geological reservoirs can trigger seismicity and induce ground deformations when the injection increases the fluid pressure in the vicinity of potentially seismic faults. The increased fluid pressure reduces the strength against fault slip, allowing the stored elastic energy to be released in seismic events that can produce felt ground accelerations. Here, we seek to explore the likelihood ground motions induced by a CO ₂ injection using hydromechanical modelling with multiphase fluid flow and dynamic rupture, including fault-frictional weakening. We extend the previous work of Cappa and Rutqvist, in which activation of a normal fault at critical stress may be possible for fast rupture nucleating by localized increase in fluid pressure and large decrease in fault friction. In this paper, we include seismic wave propagation generated by the rupture. For our assumed system and injection rate, simulations show that after a few days of injection, a dynamic fault rupture of few centimetres nucleates at the base of the CO ₂ reservoir and grows bilaterally, both toward the top of the reservoir and outside. The rupture ismore » asymmetric and affects a larger zone below the reservoir where the rupture is self-propagating (without any further pressure increase) as a result of fault-strength weakening. The acceleration and deceleration of the rupture generate waves and result in ground accelerations (~0.1–0.6 g) consistent with observed ground motion records. Finally, the maximum ground acceleration is obtained near the fault, and horizontal accelerations are generally markedly higher than vertical accelerations.« less

Authors:

Cappa, Frédéric ^[1]; Rutqvist, Jonny ^[2]

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+ Show Author Affiliations

1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division; Univ. of California, Berkeley, CA (United States); University of Nice Sophia-Antipolis, Cote d Azur Observatory, Sophia-Antipolis (France). GeoAzur
2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division; Univ. of California, Berkeley, CA (United States)

Publication Date:

2012-09-01

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Fossil Energy (FE)

OSTI Identifier:

1407161

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Journal Article: Accepted Manuscript

Journal Name:

Geophysical Journal International

Additional Journal Information:

Journal Volume: 190; Journal Issue: 3; Journal ID: ISSN 0956-540X

Publisher:

Oxford University Press

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; Dynamics and mechanics of faulting; Earthquake dynamics; Mechanics, theory, and modeling; Permeability and porosity; Geomechanics