scholarly journals Carbonaceous Materials in the Fault Zone of the Longmenshan Fault Belt: 2. Characterization of Fault Gouge from Deep Drilling and Implications for Fault Maturity

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 393 ◽  
Author(s):  
Li-Wei Kuo ◽  
Jyh-Rou Huang ◽  
Jiann-Neng Fang ◽  
Jialiang Si ◽  
Sheng-Rong Song ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Active Fault ◽  
Slip Surface ◽  
Frictional Heating ◽  
Damage Zone ◽  
Temperature Perturbation ◽  
Carbonaceous Materials ◽  
Longmenshan Fault ◽  
Fault Belt

In recent works on the determination of graphitization of carbonaceous materials (CM) within the principal slip zone (PSZ) of the Longmenshan fault (China), we demonstrated that the formation of graphite, resulted from strain and frictional heating, could be evidence of past seismic slip. Here we utilize Raman Spectroscopy of CM (RSCM) on the CM-bearing gouges in the fault zone of the Longmenshan fault belt, at the borehole depth of 760 m (FZ760) from the Wenchuan earthquake Fault Scientific Drilling project-1 (WFSD-1), to quantitatively characterize CM and further retrieve ancient fault deformation information in the active fault. RSCM shows that graphitization of CM is intense in the fault core with respect to the damage zone, with the graphitized carbon resembling those observed on experimentally formed graphite that was frictionally generated. Importantly, compared to the recognized active fault zone of the Longmenshan fault, the RSCM of measured CM-rich gouge shows a higher degree of graphitization, likely derived from high-temperature-perturbation faulting events. It implies that FZ760 accommodated numerous single-event displacement and/or at higher normal stresses and/or in the absence of pore fluid and/or along a more localized slip surface(s). Because graphite is a well-known lubricant, we surmise that the presence of the higher degree graphitized CM within FZ760 will reduce the fault strength and inefficiently accumulate tectonic stress during the seismic cycle at the current depth, and further infer a plausible mechanism for fault propagation at the borehole depth of 590 m during the Mw 7.9 Wenchuan earthquake.

scholarly journals Carbonaceous Materials in the Fault Zone of the Longmenshan Fault Belt: 1. Signatures within the Deep Wenchuan Earthquake Fault Zone and Their Implications

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 385 ◽  
Author(s):  
Li-Wei Kuo ◽  
Jyh-Rou Huang ◽  
Jiann-Neng Fang ◽  
Jialiang Si ◽  
Haibing Li ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Active Fault ◽  
Carbonaceous Materials ◽  
Coseismic Slip ◽  
Earthquake Fault ◽  
Active Fault Zone ◽  
2008 Wenchuan Earthquake ◽  
Seismic Slip ◽  
Longmenshan Fault

Graphitization of carbonaceous materials (CM) has been experimentally demonstrated as potential evidence of seismic slip within a fault gouge. The southern segment of the Longmenshan fault, a CM-rich-gouge fault, accommodated coseismic slip during the 2008 Mw 7.9 Wenchuan earthquake and potentially preserves a record of processes that occurred on the fault during the slip event. Here, we present a multi-technique characterization of CM within the active fault zone of the Longmenshan fault from the Wenchuan earthquake Fault Scientific Drilling-1. By contrast with field observations, graphite is pervasively and only distributed in the gouge zone, while heterogeneously crystallized CM are present in the surrounding breccia. The composite dataset that is presented, which includes the localized graphite layer along the 2008 Wenchuan earthquake principal slip zone, demonstrates that graphite is widely distributed within the active fault zone. The widespread occurrence of graphite, a seismic slip indicator, reveals that surface rupturing events commonly occur along the Longmenshan fault and are characteristic of this tectonically active region.

scholarly journals Carbonaceous Materials in the Longmenshan Fault Belt Zone: 3. Records of Seismic Slip from the Trench and Implications for Faulting Mechanisms

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 457 ◽  
Author(s):  
Jialiang Si ◽  
Haibing Li ◽  
Li-Wei Kuo ◽  
Jyh-Rou Huang ◽  
Sheng-Rong Song ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Companion Paper ◽  
Carbonaceous Materials ◽  
Spectrometric Data ◽  
Chemical Enrichment ◽  
Longmenshan Fault ◽  
Fault Belt ◽  
Geochemical Analyses ◽  
Fluid Penetration

In recent studies on the recognition of graphitized gouges within the principal slip zone (PSZ) of the Longmenshan fault in China, we proposed that the presence of graphite might be evidence of fault slip. Here, we characterized the clay- and carbonaceous-rich gouges of the active fault zone of the Longmenshan fault belt using samples collected from the trench at Jiulong, which was deformed during the 2008 MW-7.9 Wenchuan earthquake, to determine if graphite is present and study both the processes influencing fault behavior and the associated faulting mechanism. Mineralogical and geochemical analyses of the Jiulong trench sample show the presence of a hydrothermal mineral (i.e., dickite) integrated with dramatic relative chemical enrichment and relative depletion within a yellowish zone, suggesting the presence of vigorous high-temperature fluid–rock interactions, which are likely the fingerprint of thermal pressurization. This is further supported by the absence of carbonaceous materials (CMs) given the spectrometric data obtained. Interestingly, the Raman parameters measured near the carbonaceous-rich gouge fall within the recognized range of graphitization in the mature fault zone, implying the origin of a mature fault, as shown in the companion paper. According to both the sharp boundary within the very recent coseismic rupture zone of the 2008 MW-7.9 Wenchuan earthquake and the presence of kinetically unstable dickite, it is strongly implied that the yellow/altered gouge likely formed from a recent coseismic event as aconsequence of hydrothermal fluid penetration. We further surmise that the CM characteristics varied according to several driving reactions, e.g., transient hydrothermal heating versus long-term geological metamorphism and sedimentation.

scholarly journals Fault zone trapped waves at Longmenshan fault belt

2013 ◽  
Vol 4 (3) ◽  
pp. 48-52
Author(s):  
Sun Yi ◽  
Lai Xiaoling
Keyword(s):  
Fault Zone ◽  
Trapped Waves ◽  
Longmenshan Fault ◽  
Fault Belt

scholarly journals Coseismic fluid–rock interactions in the Beichuan-Yingxiu surface rupture zone of the Mw 7.9 Wenchuan earthquake and its implication for the fault zone transformation

2020 ◽  
Author(s):  
Yangyang Wang ◽  
Xiaoqi Gao ◽  
Sijia Li ◽  
Shiyuan Wang ◽  
Deyang Shi ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Structural Characteristics ◽  
Damage Zone ◽  
Major Elements ◽  
Rupture Zone ◽  
Surface Rupture ◽  
Fault Rock ◽  
Surface Rupture Zone ◽  
Geochemical Variations

Abstract. Mechanism of fluids in modifying mineralogy and geochemistry of the fault zone and the role of rock-fluid interaction in the faulting weakening is still debatable. Through analyzing mineralogical compositions, major elements as well as micro-structural characteristics of outcrop samples including wall rocks, low damage zone, high damage zone and oriented fault gouge samples from principal slip zone gouges, mineralogical and geochemical variations of the fault-rocks is observed from Shaba outcrop of Beichuan-Yingxiu surface rupture zone of the Mw 7.9 Wenchuan earthquake, China. The element enrichment/depletion pattern of fault rock shows excellent consistency with the variation pattern of minerals in terms of the notable feldspar alteration and decomposition, decarbonization, coseismic illitization, and chloritization that occurs in the fault zone. The Isocon analysis indicates that the overall mass loss amount of the Shaba fault zone is ranked as low damage zone 

Fine Seismic Structure Under the Longmenshan Fault Zone and the Mechanism of the Large Wenchuan Earthquake

2009 ◽  
Vol 52 (1) ◽  
pp. 112-119 ◽  
Author(s):  
Jian-She LEI ◽  
Da-Peng ZHAO ◽  
Jin-Rong SU ◽  
Guang-Wei ZHANG ◽  
Feng Li
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Seismic Structure ◽  
Longmenshan Fault Zone ◽  
Longmenshan Fault

Continuous Permeability Measurements Record Healing Inside the Wenchuan Earthquake Fault Zone

Science ◽  
2013 ◽  
Vol 340 (6140) ◽  
pp. 1555-1559 ◽  
Author(s):  
Lian Xue ◽  
Hai-Bing Li ◽  
Emily E. Brodsky ◽  
Zhi-Qing Xu ◽  
Yasuyuki Kano ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Damage Zone ◽  
Fault Zones ◽  
Deep Borehole ◽  
Earthquake Fault ◽  
Hydraulic Diffusivity ◽  
The Wenchuan Earthquake ◽  
Direct Measurements ◽  
Observation Period

Permeability controls fluid flow in fault zones and is a proxy for rock damage after an earthquake. We used the tidal response of water level in a deep borehole to track permeability for 18 months in the damage zone of the causative fault of the 2008 moment magnitude 7.9 Wenchuan earthquake. The unusually high measured hydraulic diffusivity of 2.4 × 10−2square meters per second implies a major role for water circulation in the fault zone. For most of the observation period, the permeability decreased rapidly as the fault healed. The trend was interrupted by abrupt permeability increases attributable to shaking from remote earthquakes. These direct measurements of the fault zone reveal a process of punctuated recovery as healing and damage interact in the aftermath of a major earthquake.

Coupling fraction and relocking process of the Longmenshan Fault Zone following the 2008 Mw7.9 Wenchuan earthquake

2020 ◽  
Vol 137 ◽  
pp. 101730
Author(s):  
Jing Zhao ◽  
Jinwei Ren ◽  
Jie Liu ◽  
Zaisen Jiang ◽  
Xiaoxia Liu ◽  
...  
Keyword(s):  
Wenchuan Earthquake ◽  
Fault Zone ◽  
Longmenshan Fault Zone ◽  
Longmenshan Fault
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