The Wenchuan Earthquake Fault Scientific Drilling (WFSD) Project

Xu, Zhiqin; Li, Haibing

doi:10.1007/978-981-13-8015-0_3

Cited by 8 publications

(3 citation statements)

References 53 publications

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“…During the Wenchuan earthquake (Mw 7.9, 2008), two surface ruptures occurred along the Anxian‐Guanxian and Yingxiu‐Beichuan faults [ Li et al ., ]. To investigate the physical properties in large displacements of the ruptured faults and the mechanism of the Wenchuan earthquake faulting, the Wenchuan Earthquake Fault Scientific Drilling (WFSD) was initiated immediately after the Wenchuan earthquake [ Xu et al ., ]. Microstructural, geochemical, and geophysical studies from surface ruptures and WFSD cores demonstrate that the pseudotachylytes, fresh fault gouge, and gouge graphitization constitute rock records of powerful earthquakes [ Kuo et al ., ; Li et al ., ; Wang et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Rock record and magnetic response to large earthquakes within Wenchuan Earthquake Fault Scientific Drilling cores

Zhang

Sun

et al. 2017

Geochem Geophys Geosyst

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Fault‐related pseudotachylytes are often considered to be produced by large seismic events. To investigate the rock record and magnetic response to large earthquakes within cores from the Wenchuan Earthquake Fault Scientific Drilling borehole 2 (WFSD‐2), we carried out microstructural, geochemical, and rock‐magnetic analyses of representative cores. Based on microstructural observations and powder X‐ray diffraction analyses, we found 21 layers of melt‐origin pseudotachylytes from 579.62 to 599.31 m‐depth in the cores. The presence of early‐formed pseudotachylyte fragments in the new layer suggests that seismic faulting processes exploited the same fault strand more than once. Pseudotachylyte veins have higher values of magnetic susceptibility relative to wall rocks. Rock‐magnetic results indicate that the magnetic minerals within the pseudotachylyte veins are magnetite with varying amounts of paramagnetic minerals. Magnetic hysteresis loops show that a reduction of the grain size of ferromagnetic minerals is not a plausible explanation for the higher magnetic susceptibility values in pseudotachylyte veins. Rock‐magnetic analyses indicate that frictional heating (>500°C) occurred in the pseudotachylyte veins during large earthquakes. The resulting high temperatures induced thermal decomposition of paramagnetic minerals, forming magnetite and contributing to the higher magnetic susceptibility values. Different generations of pseudotachylytes and numerous high magnetic susceptibility zones together demonstrate that ancient powerful earthquakes may have occurred repeatedly in the Longmen Shan thrust belt.

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Section: Introductionmentioning

confidence: 99%

Rock record and magnetic response to large earthquakes within Wenchuan Earthquake Fault Scientific Drilling cores

Zhang

Sun

et al. 2017

Geochem Geophys Geosyst

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“…Among the widely reported fault weakening mechanisms, such as thermal pressurization, frictional melting, flash heating, thermal decomposition, nanoparticle lubrication and so on, thermal pressurization has been proposed as the paramount dynamic weakening mechanism during the 2008 Wenchuan earthquake (e.g., Chen, Yang, Duan, et al, 2013;Duan et al, 2017;Xu & Li, 2019). Thanks to the presence of multiple generations of pseudotachylyte outcropped along the Yingxiu-Beichuan fault zone, H. Wang et al (2015) suggested that friction melt lubrication, thermal pressurization, and mechanical lubrication could operate together during the coseismic slip.…”

Section: Implications For Fault Slip Weakeningmentioning

confidence: 99%

Coseismic Frictional Heating With Concomitant Hydrothermal Fluid Circulation Revealed by Rock Magnetic Properties of Fault Rocks From the Rupture of the 2008 Wenchuan Earthquake, China

Yan,

Zhang,

Wang

et al. 2023

Geochem Geophys Geosyst

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Coseismic frictional heating and associated hydrothermal fluid circulation play an essential role in the dynamic weakening of seismic faults. However, temperature rise induced by frictional heating during an earthquake is still difficult to constrain. Magnetic properties of fault rocks convey abundant information on faulting processes. In this study, detailed rock magnetic measurements in combination with electron microscopic observations are conducted on fault rocks and protoliths from the Shaba outcrop (Beichuan County) on the Yingxiu‐Beichuan Fault ruptured during the 2008 Wenchuan Mw 7.9 earthquake. Results show that protoliths and the majority of fault rocks are dominated by paramagnetic pyrite and/or Fe‐bearing clay minerals; in contrast, the presence of pyrrhotite and goethite is confined to the fault gouges just next to the principal slip surface. Pyrrhotite is a product of pyrite alteration at high temperatures (>500°C) induced by seismic frictional heating during earthquake slip. Meanwhile, the goethite implies the presence of coseismic hot fluids within the fault zone. All these observations strongly suggest the occurrence of thermal pressurization as a plausible mechanism of coseismic fault weakening during the Wenchuan earthquake.

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“…The content of mercury is mainly related to the degree of rock fracture and the clay mineral inside. The distribution of mercury concentration indicates that deep fluid may have played a role in the occurrence of the Wenchuan M 8.0 earthquake [39,40]. The extent of disintegration and the opening and closure of the fracture can cause uneven distribution of mercury, and there usually is a higher mercury concentration in the hanging wall of the fault [41].…”

Section: Mercurymentioning

confidence: 99%

Geo-Chemical Techniques for Earthquake Forecasting in Nigeria

Wuyep¹,

Kadiri²,

Monday³

et al. 2021

AJGR

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Regardless of the doubt caused by some rounds on the impossibility of earthquake forecast, more and more countries, even at the highest governmental levels, realize that doing nothing is the ostrich position of dread before the real difficulties associated with the creation of a real forecasting system. Nigeria in times past was believed to be aseismic. However, the seismic record of Nigeria from 1933-2021 have demonstrated in contrast to the idea, numerous quakes have been recorded in Nigeria throughout the years. With the development of observation techniques and theoretical knowledge of geochemistry, geochemical observation of faults gas has become a hotspot once more in recent years. Rn, Hg, H2, etc., are used for geochemical observations. 222Rn has a half-life of 3.825 days, a magnitude 5.0 earthquake will be detected through precursory phenomena at a distance not greater than 142 km. Mercury and other elements are used as important detectors for earthquake prediction and they play an important role in revealing the relationship between fluid in the fault zone and the occurrence of earthquakes, the range for a magnitude 5.0 earthquake is limited to 200 km. Hydrogen concentrations have been monitored for precursory variations in many fault systems, using either discrete sampling and laboratory analysis or continuous monitoring of ground gas, using hydrogen-sensitive fuel cells. Precursory changes in groundwater chemistry are often attributed to the mixing of fluids from two or more chemically distinct aquifers, the physical mechanism responsible for the mixing of fluids is, however, not well established.

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The Wenchuan Earthquake Fault Scientific Drilling (WFSD) Project

Cited by 8 publications

References 53 publications

Rock record and magnetic response to large earthquakes within Wenchuan Earthquake Fault Scientific Drilling cores

Rock record and magnetic response to large earthquakes within Wenchuan Earthquake Fault Scientific Drilling cores

Coseismic Frictional Heating With Concomitant Hydrothermal Fluid Circulation Revealed by Rock Magnetic Properties of Fault Rocks From the Rupture of the 2008 Wenchuan Earthquake, China

Geo-Chemical Techniques for Earthquake Forecasting in Nigeria

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