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Pulse-like ruptures induced by low-velocity fault zones

Huang, Yihe and Ampuero, Jean-Paul (2011) Pulse-like ruptures induced by low-velocity fault zones. Journal of Geophysical Research B, 116 (B12). Art. No. B12307. ISSN 0148-0227. doi:10.1029/2011JB008684.

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Low-velocity fault zones (LVFZs) are found in most mature faults. They are usually 100–400 m wide and have ~20%–60% wave velocity reductions relative to the country rock. To study the effect of LVFZs on earthquake rupture and the radiated wavefield, we conducted two-dimensional (2-D) simulations of dynamic rupture on faults that bisect a LVFZ, considering a range of velocity reductions and widths. Most earthquakes apparently have slip rise times much shorter than their overall rupture duration. A number of dynamic mechanisms for such pulse-like ruptures have been proposed, including frictional self-healing, fault strength heterogeneities, and bimaterial effects. We find that ruptures in LVFZs with strong enough wave velocity contrast behave as pulses. These pulses are generated by fault locking induced by waves reflected from the boundaries of the LVFZ. This mechanism of pulse generation is robust to variations of initial stress, smoothness of the LVFZ structure, rupture mode, and exclusion of frictional healing. Moreover, we find that LVFZs can generate complex rupture patterns. LVFZs with low-velocity reduction induce multiple rupture fronts involving coexisting pulses and cracks. LVFZs with certain widths can accelerate the transition to supershear rupture speed. These additional effects of LVFZs on dynamic rupture can contribute to the complexity of high-frequency ground motions.

Item Type:Article
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Ampuero, Jean-Paul0000-0002-4827-7987
Additional Information:© 2011 by the American Geophysical Union. Received 18 July 2011; revised 4 October 2011; accepted 6 October 2011; published 13 December 2011. This work was supported by the NSF (grant EAR-0944288). We thank Steven Day and Luis Dalguer for providing the DFM code for our benchmarks. We also thank Steven Day and an anonymous reviewer for their helpful suggestions.
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:dynamic rupture; ground motion; low-velocity fault zone; slip pulse
Issue or Number:B12
Record Number:CaltechAUTHORS:20120125-084055135
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Official Citation:Huang, Y., and J.-P. Ampuero (2011), Pulse-like ruptures induced by low-velocity fault zones, J. Geophys. Res., 116, B12307, doi:10.1029/2011JB008684
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:28952
Deposited By: Tony Diaz
Deposited On:21 Mar 2012 21:12
Last Modified:09 Nov 2021 17:02

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