On the evolution of elastic properties during laboratory stick‐slip experiments spanning the transition from slow slip to dynamic rupture

Abstract

The physical mechanisms governing slow earthquakes remain unknown, as does the relationship between slow and regular earthquakes. To investigate the mechanism(s) of slow earthquakes and related quasi‐dynamic modes of fault slip we performed laboratory experiments on simulated fault gouge in the double direct shear configuration. We reproduced the full spectrum of slip behavior, from slow to fast stick slip, by altering the elastic stiffness of the loading apparatus (k) to match the critical rheologic stiffness of fault gouge (kc). Our experiments show an evolution from stable sliding, when k > kc, to quasi‐dynamic transients when k ~ kc, to dynamic instabilities when k < kc. To evaluate the microphysical processes of fault weakening we monitored variations of elastic properties. We find systematic changes in P wave velocity (Vp) for laboratory seismic cycles. During the coseismic stress drop, seismic velocity drops abruptly, consistent with observations on natural faults. In the preparatory phase preceding failure, we find that accelerated fault creep causes a Vp reduction for the complete spectrum of slip behaviors. Our results suggest that the mechanics of slow and fast ruptures share key features and that they can occur on same faults, depending on frictional properties. In agreement with seismic surveys on tectonic faults our data show that their state of stress can be monitored by Vp changes during the seismic cycle. The observed reduction in Vp during the earthquake preparatory phase suggests that if similar mechanisms are confirmed in nature high‐resolution monitoring of fault zone properties may be a promising avenue for reliable detection of earthquake precursors.

Preseismic Fault Creep and Elastic Wave Amplitude Precursors Scale With Lab Earthquake Magnitude for the Continuum of Tectonic Failure Modes

“…This wavelet represents the transducer response to the first arrival rather than the P-wave coda used by previous studies (eg. Scuderi et al, 2016;Singh et al, 2019), which represents accumulated effects of multiple reflections through frictional interfaces and the bulk ( Figure 4 in Tinti et al, 2016). For more detailed experimental methods, we refer readers to Shreedharan et al (2019) and Supporting Information S1.…”

Controlling Anthropogenic and Natural Seismicity: Insights From Active Stabilization of the Spring‐Slider Model

“…Nevertheless, its thickness is linked with the softening response of the system, that is, the reduction of friction in function of slip, rate of slip, and other variables related to multiphysical couplings. This region of extreme shearing usually consisted of ultracataclastic materials, and it has a complex structure (Ben‐Zion & Sammis, ; Brodie et al, ) due to various physicochemical phenomena that take place during preseismic slip and coseismic slip (see Anthony & Marone, ; Rattez et al, , , ; Reches & Lockner, ; Scuderi et al, ; Tinti et al, , among others). As a result, the apparent friction, F , does not depend only on the extent and the rate of slip, but also on the evolution of the microstructural network, the grain size, the presence and pressure of interstitial fluids, the temperature, time (state) and the reactivation of chemical reactions (Brantut & Sulem, ; Veveakis et al, , , among others).…”

Slow and fast ruptures on a laboratory fault controlled by loading characteristics

“…This stability transition, described in section 2, marks a balance between the rate of elastic energy release and the rate of frictional strength loss. Rich behavior that includes slow slip events has been demonstrated numerically [ Gu et al ., ; Rice and Gu , ] and experimentally [ Leeman et al ., ; Tinti et al ., ]. Continuous fault models have utilized transitional behavior to describe slow slip events [ Liu and Rice , , ] and both fast and slow ruptures on the same VW fault patch [e.g., Veedu and Barbot , ; Chen and Lapusta , ].…”