Time-Dependent Compaction as a Mechanism for Regular Stick-Slips
MPA van den Ende and AR Niemeijer, GEOPHYSICAL RESEARCH LETTERS, 45, 5959-5967 (2018).
Owing to their destructive potential, earthquakes receive considerable attention from laboratory studies. In friction experiments, stick-slips are studied as the laboratory equivalent of natural earthquakes, and numerous attempts have been made to simulate stick-slips numerically using the discrete element method (DEM). However, while laboratory stick-slips commonly exhibit regular stress drops and recurrence times, stick-slips generated in DEM simulations are highly irregular. This discrepancy highlights a gap in our understanding of stick-slip mechanics, which propagates into our understanding of earthquakes. In this work, we show that regular stick-slips emerge in DEM when time- dependent compaction by pressure solution is considered. We further show that the stress drop and recurrence time of stick-slips are directly controlled by the kinetics of pressure solution. Since compaction is known to operate in faults, this mechanism for frictional instabilities directly relates to natural seismicity. Plain Language Summary Earthquakes have a big impact on the society and are therefore intensively studied in laboratory settings. The study of laboratory- scale earthquakes, the so-called stick-slips, generates new insights into the origin and behavior of earthquakes in nature. At present, computer simulations of stick-slips have not been able to reproduce prominent laboratory observations, which shows that the origin of stick- slips, and of natural earthquakes, is not yet fully understood. In this work, we present computer simulations that succeed to reproduce the laboratory observations, thereby revealing that time-dependent compaction is of great importance to stick-slips and natural earthquakes. These results help to further understand the complex behavior of earthquakes in nature.
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