期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：51
DOI：10.1073/pnas.2023433118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Fluids present in the Earth’s crust promote earthquakes, as well as a variety of aseismic slip events, both in natural tectonic settings and potentially due to industrial activities, such as wastewater disposal, geothermal energy production, and CO
2 storage. To study the physical processes linking fluids and slip motion, we have devised a laboratory earthquake setup capable of injecting fluid onto a simulated fault and monitoring the resulting slip on a wide range of temporal and spatial scales. Our findings indicate that faster injection rates result in lower fluid pressure at rupture initiation, highlighting the role of fluid injection rate in inducing seismic or aseismic slip events. We also find that the presence of fluids significantly affects the dynamic rupture propagation.
Fluids are known to trigger a broad range of slip events, from slow, creeping transients to dynamic earthquake ruptures. Yet, the detailed mechanics underlying these processes and the conditions leading to different rupture behaviors are not well understood. Here, we use a laboratory earthquake setup, capable of injecting pressurized fluids, to compare the rupture behavior for different rates of fluid injection, slow (megapascals per hour) versus fast (megapascals per second). We find that for the fast injection rates, dynamic ruptures are triggered at lower pressure levels and over spatial scales much smaller than the quasistatic theoretical estimates of nucleation sizes, suggesting that such fast injection rates constitute dynamic loading. In contrast, the relatively slow injection rates result in gradual nucleation processes, with the fluid spreading along the interface and causing stress changes consistent with gradually accelerating slow slip. The resulting dynamic ruptures propagating over wetted interfaces exhibit dynamic stress drops almost twice as large as those over the dry interfaces. These results suggest the need to take into account the rate of the pore-pressure increase when considering nucleation processes and motivate further investigation on how friction properties depend on the presence of fluids.
