Department of Geosciences, and Energy Institute Center for Geomechanics, Geofluids and Geohazards, Pennsylvania State University, University Park, PA 16802, USA.
Science. 2013 Sep 13;341(6151):1229-32. doi: 10.1126/science.1239577. Epub 2013 Aug 15.
Earthquakes normally occur as frictional stick-slip instabilities, resulting in catastrophic failure and seismic rupture. Tectonic faults also fail in slow earthquakes with rupture durations of months or more, yet their origin is poorly understood. Here, we present laboratory observations of repetitive, slow stick-slip in serpentinite fault zones and mechanical evidence for their origin. We document a transition from unstable to stable frictional behavior with increasing slip velocity, providing a mechanism to limit the speed of slow earthquakes. We also document reduction of P-wave speed within the active shear zone before stick-slip events. If similar mechanisms operate in nature, our results suggest that higher-resolution studies of elastic properties in tectonic fault zones may aid in the search for reliable earthquake precursors.
地震通常发生在摩擦的粘滑不稳定性中，导致灾难性的破坏和地震破裂。构造断层也会在持续数月或更长时间的慢地震中失效，但它们的起源还不太清楚。在这里，我们展示了蛇纹石化断层带中重复的、缓慢的粘滑的实验室观测结果，以及它们起源的机械证据。我们记录了随着滑移速度的增加，摩擦行为从不稳定到稳定的转变，为限制慢地震速度提供了一种机制。我们还记录了在粘滑事件之前，主动剪切带内的 P 波速度的降低。如果类似的机制在自然界中起作用，我们的结果表明，对构造断层带弹性性质的更高分辨率研究可能有助于寻找可靠的地震前兆。
