A mixed seismic-aseismic stress release episode in the Andean subduction zone

作者：Villegas Lanza J C^*; Nocquet J M^*; Rolandone F; Vallee M; Tavera H; Bondoux F; Tran T; Martin X; Chlieh M

来源：Nature Geoscience, 2016, 9(2): 150-+.

DOI：10.1038/NGEO2620

In subduction zones, stress is released by earthquakes and transient aseismic slip. The latter falls into two categories: slow slip and afterslip. Slow-slip events emerge spontaneously during the interseismic phase, and show a progressive acceleration of slip with a negligible contribution of synchronous tremors or microseismicity to the energy, or moment release(1-12). In contrast, afterslip occurs immediately after large and moderate earthquakes, decelerates over time, and releases between 20 and 400% of the moment released by the preceding earthquake(13-18). Here we use seismic and GPS data to identify transient aseismic slip that does not fit into either of these categories. We document a seismic-aseismic slip sequence which occurred at shallow depths along a weakly coupled part of the Andean subduction zone(19) in northern Peru and lasted seven months. The sequence generated several moderate earthquakes that together account for about 25% of the total moment released during the full sequence, equivalent to magnitude 6.7. Transient slip immediately followed two of the earthquakes, with slip slowing at a logarithmic rate. Considered separately, the moment released by transient slip following the second earthquake was more than 1,000% of the moment released during the earthquake itself, a value incompatible with classical models of afterslip. Synchronous seismic swarms and aseismic slipmay therefore definea stress-release process that is distinct from slow-slip events and afterslip.

• 出版日期2016-2