Abstract
Basalt is a major component of the earth and moon crust.Mineral composition and temperature influence frictional instability and thus the potential for seismicity on basaltic faults.We performed velocity-stepping shear experiments on basalt gouges at a confining pressure of 100 MPa,temperatures in the range of 100-400 °C and with varied obsidian mass fractions of 0-100%under wet/dry conditions to investigate the frictional strength and stability of basaltic faults.We observe a transition from velocity-neutral to velocity-weakening behaviors with increasing obsidian content.The frictional stabil-ity response of the mixed obsidian/basalt gouges is characterized by a transition from velocity-strengthening to velocity-weakening at 200°C and another transition to velocity-strengthening at tem-peratures>300°C.Conversely,frictional strengths of the obsidian-bearing gouges are insensitive to tem-perature and wet/dry conditions.These results suggest that obsidian content dominates the potential seismic response of basaltic faults with the effect of temperature controlling the range of seismogenic depths.Thus,shallow moonquakes tend to occur in the lower lunar crust due to the corresponding antic-ipated higher glass content and a projected temperature range conducive to velocity-weakening behav-ior.These observations contribute to a better understanding of the nucleation mechanism of shallow seismicity in basaltic faults.
基金项目
National Natural Science Foundation of China(42320104003)
National Natural Science Foundation of China(42107163)
Fundamental Research Funds for the Central Universities()
维普
万方数据