资源环境科技发展态势分析平台

The origins of tremors and their relation to fault slip and impending earthquakes remain unclear. Laboratory studies on tremor-like acoustic emission events generated during preslip may shed some light on the above issues. We conducted stick-slip experiments and observed tremor-like events and preslip in the laboratory. The results show the following. (1) The dominant frequency of tremor-like events increases with accelerating preslip. (2) The evolution of tremor-like events is spatiotemporally consistent with that of preslip. (3) Interactions between preslip and high-frequency events indicate the formation of a positive feedback effect between the expansion of preslip and failure of asperities, which leads to stick-slip instability. Thus, we propose that tremors may be caused by stress variations derived from asperity interactions along fault surfaces at dry conditions. The increasing dominant frequency of tremors may imply the accelerating preslip of an upcoming earthquake.

Plain Language Summary The origins of tremors and their relation to fault slip as well as the impending earthquakes are still unclear. Experimental studies on the relationship between preslip and tremor-like acoustic emission events may shed some light on understanding the above issues. We conducted stick-slip experiments on a granodiorite sample. Acoustic emission signals radiated from the sample were continuously recorded at a sampling rate of 3 MHz during the experiment. Fault slip was observed at a sampling rate of 1 kHz with 1,771 measurement points spacing of 0.2 mm along the fault. By doing this, the spatiotemporal evolution of slip velocity and preslip zones, the interaction between preslip and high-frequency acoustic emission events, and the evolution of low-frequency tremor-like acoustic emission events were observed. The increase in dominant frequency of the tremor-like events with accelerating preslip and the correlated spatiotemporal evolution between preslip and tremor-like events both indicate that tremor can be caused by the stress variation derived from the asperity interaction on the fault surface at dry conditions. Furthermore, the increase in the dominant frequency of tremors may be a signature for the accelerating preslip of the upcoming earthquake.