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 velocitystepping shear...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 velocitystepping shear experiments on basalt gouges at a confining pressure of 100 MPa,temperatures in the range of 100-400℃ 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 stability response of the mixed obsidian/basalt gouges is characterized by a transition from velocitystrengthening to velocity-weakening at 200℃ and another transition to velocity-strengthening at temperatures>300℃.Conversely,frictional strengths of the obsidian-bearing gouges are insensitive to temperature 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 anticipated higher glass content and a projected temperature range conducive to velocity-weakening behavior.These observations contribute to a better understanding of the nucleation mechanism of shallow seismicity in basaltic faults.展开更多
There are essentially six sources for obsidians in the Mediterranean Basin： Mount Arci in Sardinia, the islands of Lipari and Pantelleria in Sicily and Palmarola in Latium, as well as the islands of Melos and Gyali i...There are essentially six sources for obsidians in the Mediterranean Basin： Mount Arci in Sardinia, the islands of Lipari and Pantelleria in Sicily and Palmarola in Latium, as well as the islands of Melos and Gyali in the south-eastern part of Greece. Identification and quantification of principal and trace elements which compose this volcanic glass allow source tracking. The present study proposes a investigation methodology, which was developed on a sample set composed by archaeological obsidian findings from Neolithic sites in Latium; three different analytical techniques are compared： SEM-EDXS, ED-XRF and LA-ICP-MS, in order to gather a wide data set to be compared with data in literature and to be processed by Principal Component Analysis （PCA） for assigning a provenance to each find.展开更多
基金funded by the National Natural Science Foundation of China(Nos.42320104003 and 42107163)the Funda mental Research Funds for the Central Universities.Derek Elsworth acknowledges support from the G.Albert Shoemaker endowment.
文摘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 velocitystepping shear experiments on basalt gouges at a confining pressure of 100 MPa,temperatures in the range of 100-400℃ 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 stability response of the mixed obsidian/basalt gouges is characterized by a transition from velocitystrengthening to velocity-weakening at 200℃ and another transition to velocity-strengthening at temperatures>300℃.Conversely,frictional strengths of the obsidian-bearing gouges are insensitive to temperature 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 anticipated higher glass content and a projected temperature range conducive to velocity-weakening behavior.These observations contribute to a better understanding of the nucleation mechanism of shallow seismicity in basaltic faults.
文摘There are essentially six sources for obsidians in the Mediterranean Basin： Mount Arci in Sardinia, the islands of Lipari and Pantelleria in Sicily and Palmarola in Latium, as well as the islands of Melos and Gyali in the south-eastern part of Greece. Identification and quantification of principal and trace elements which compose this volcanic glass allow source tracking. The present study proposes a investigation methodology, which was developed on a sample set composed by archaeological obsidian findings from Neolithic sites in Latium; three different analytical techniques are compared： SEM-EDXS, ED-XRF and LA-ICP-MS, in order to gather a wide data set to be compared with data in literature and to be processed by Principal Component Analysis （PCA） for assigning a provenance to each find.
