Abstract
The depth extent of the crustal seismogenic zone is closely related to the size of earthquakes. The mechanisms that control the depth of the lower transition of the seismogenic zone are important issues in seismology and disaster mitigation. Laboratory studies have shown that the mechanism of earthquake nucleation is controlled by the frictional properties of fault materials. We measured the velocity dependences of the steady-state friction of quartz and feldspar, two major components of crustal rocks, under dry and wet conditions at temperatures up to 600 °C. In the presence of water, the temperature range over which the velocity dependence of steady-state friction was negative was wider for feldspar than for quartz, thus indicating that the temperature range of earthquake nucleation is wider for feldspar than for quartz. Considering that temperature increases with depth, our findings indicate that the material properties of feldspar likely play a dominant role in limiting the depth extent of the seismogenic zone.
Highlights
The magnitude of earthquakes is directly related to the subsurface depth range over which they nucleate, that is, the depth extent or thickness of the seismogenic zone
Based on the velocity dependence of steady-state friction, which controls the seismic or aseismic behavior of crustal material, we provide here laboratory evidence of the influence of the material properties of quartz and feldspar on the depth extent of the seismogenic zone
Effect of water on velocity dependence of steady-state friction The differences of the values of (a – b) that we identified for dry and wet samples of quartz and feldspar demonstrated that the presence of water strongly influence their frictional properties
Summary
The magnitude of earthquakes is directly related to the subsurface depth range over which they nucleate, that is, the depth extent or thickness of the seismogenic zone. Thicker seismogenic zones produce higher magnitude earthquakes that can have disastrous consequences for human society. Earthquakes nucleate only in the parts of faults that lie within the seismogenic zone. Understanding what determines the depth extent of the seismogenic zone, especially the depth of the lower stability transition, is a critical issue in seismology. In the shallow parts of faults, the upper transition of the seismogenic zone is less variable than in the lower parts; here, we concentrated our Masuda et al Progress in Earth and Planetary Science (2019) 6:50 laboratory are seldom met in nature, so models must be used with care
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