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| 1 | Internal structure of Longmenshan fault zone at Hongkou outcrop,Sichuan,China,that caused the 2008 Wenchuan earthquake显示文摘This paper reports the internal structures of the Beichuan fault zone of Longmenshan fault system that caused the 2008 Wenchuan earthquake,at an outcrop in Hongkou,Sichuan province,China.Present work is a part of comprehensive project of Institute of Geology,China Earthquake Administration,trying to understand deformation processes in Longmenshan fault zones and eventually to reproduce Wenchuan earthquake by modeling based on measured mechanical and transport properties.Outcrop studies could be integrated with those performed on samples recovered from fault zone drilling,during the Wenchuan Earthquake Fault Scientific Drilling(WFSD) Project,to understand along-fault and depth variation of fault zone properties.The hanging wall side of the fault zone consists of weakly-foliated,clayey fault gouge of about 1 m in width and of several fault breccia zones of 30-40 m in total width.We could not find any pseudotachylite at this outcrop.Displacement during the Wenchuan earthquake is highly localized within the fault gouge layer along narrower slipping-zones of about 10 to 20 mm in width.This is an important constraint for analyzing thermal pressurization,an important dynamic weakening mechanism of faults.Overlapping patterns of striations on slickenside surface suggest that seismic slip at a given time occurred in even narrower zone of a few to several millimeters,so that localization of deformation must have occurred within a slipping zone during coseismic fault motion.Fault breccia zones are bounded by thin black gouge layers containing amorphous carbon.Fault gouge contains illite and chlorite minerals,but not smectite.Clayey fault gouge next to coseismic slipping zone also contains amorphous carbon and small amounts of graphite.The structural observations and mineralogical data obtained from outcrop exposures of the fault zone of the Wenchuan earthquake can be compared with those obtained from the WFSD-1 and WFSD-2 boreholes, which have been drilled very close to the Hongkou outcrop.The presence of carbon and graphite,observed next to the slipping-zone,may affect the mechanical properties of the fault and also provide useful information about coseismic chemical changes. | Tetsuhiro Togo Toshihiko Shimamoto Shengli Ma Xueze Wen Honglin He | 2011 | Earthquake Science2011，24，3： | 19 |
| 2 | High-velocity frictional behavior of Longmenshan fault gouge from Hongkou outcrop and its implications for dynamic weakening of fault during the 2008 Wenchuan earthquake显示文摘High-velocity friction experiments were conducted on clayey fault gouge collected from Hongkou outcrop of Beichuan fault,located at the southwestern part of Longmenshan fault system that caused the disastrous 2008 Wenchuan earthquake.The ultimate purpose of this study is to reproduce this earthquake by modeling based on measured frictional properties.Dry gouge of about 1 mm in thickness was deformed dry at slip rates of 0.01 to 1.3 m/s and at normal stresses of 0.61 to 3.04 MPa,using a rotary-shear high-velocity frictional testing machine.The gouge displays slip weakening behavior as initial peak friction decays towards steady-state values after a given displacement.Both peak friction and steady-state friction remain high at slow slip rates are examined and gouge only exhibits dramatic weakening at high slip rates,with steady-state friction coefficient values of about 0.1 to 0.2.Specific fracture energy ranges from 1 to 4 MN/m in our results and this is of the same order as seismically determined values.Low friction coefficients measured on experimental faults are in broad agreement with lack of thermal anomaly observed from temperature measurements in WFSD-1 drill hole(Wenchuan Earthquake Fault Scientific Drilling Project),which can be explained by even smaller friction coefficient for the Wenchuan earthquake fault.High-velocity friction experiments with pore water needs to be done to see if even smaller friction is attained or not.Shiny slickenside surfaces form at high slip rates,but not at slow slip rates. Slip zone with slickenside surface changes its color to dark brown and forms duplex-like microstructures,which are similar to those microstructures found in the fault gouges from the Hongkou outcrop.Detailed comparisons between experimentally deformed gouge samples and WFSD drill cores in the future will reveal how much we could reproduce the dynamic weakening processes in operation in fault zones during Wenchuan earthquake at present. | Tetsuhiro Togo Toshihiko Shimamoto Shengli Ma Takehiro Hirose | 2011 | Earthquake Science2011，24，3： | 12 |
| 3 | A rotary-shear low to high-velocity friction apparatus in Beijing to study rock friction at plate to seismic slip rates显示文摘This paper reviews 19 apparatuses having highvelocity capabilities,describes a rotary-shear low to highvelocity friction apparatus installed at Institute of Geology,China Earthquake Administration,and reports results from velocity-jump tests on Pingxi fault gouge to illustrate technical problems in conducting velocity-stepping tests at high velocities.The apparatus is capable of producing plate to seismic velocities(44 mm/a to 2.1 m/s for specimens of 40 mm in diameter),using a 22 kW servomotor with a gear/belt system having three velocity ranges.A speed range can be changed by 103 or 106by using five electromagnetic clutches without stopping the motor.Two cam clutches allow fivefold velocity steps,and the motor speed can be increased from zero to 1,500 rpm in 0.1–0.2 s by changing the controlling voltage.A unique feature of the apparatus is a large specimen chamber where different specimen assemblies can be installed easily.In addition to a standard specimen assembly for friction experiments,two pressure vessels were made for pore pressures to 70 MPa;one at room temperature and the other at temperatures to 500 °C.Velocity step tests are needed to see if the framework of rate-and-state friction is applicable or not at high velocities.We report results from velocity jump tests from 1.4 mm/s to 1.4 m/s on yellowish gouge from a Pingxi fault zone,located at the northeastern part of the Longmenshan fault system that caused the 2008 Wenchuan earthquake.An instantaneous increase in friction followed by dramatic slip weakening was observed for the yellowish gouge with smooth sliding surfaces of host rock,but no instantaneous response was recognized for the same gouge with roughened sliding surfaces.Instantaneous and transient frictional properties upon velocity steps cannot be separated easily at high velocities,and technical improvements for velocity step tests are suggested. | Shengli Ma Toshihiko Shimamoto Lu Yao Tetsuhiro Togo Hiroko Kitajima | 2014 | Earthquake Science2014，27，5： | 6 |
| 4 | Prognostic significance of BMP and activin membrane-bound inhibitor in colorectal cancer显示文摘AIM: To investigate the clinical significance of BMP and activin membrane-bound inhibitor (BAMBI) which is a pseudoreceptor of transforming growth factor-beta (TGF-β) type Ⅰreceptors and acts as a negative regulator of TGF-β signaling and expression aberrantly elevated in colorectal cancers (CRCs). We studied BAMBI expression in CRCs. METHODS: We studied BAMBI expression in 183 surgically resected CRCs by immunochemical and immunoblotting analyses using a generated monoclonal anti-BAMBI antibody. Commercially available anti-β-catenin and anti-p53 antibodies were also applied for immunochemical analyses as a comparison control.RESULTS: Immunohistochemical analysis revealed that BAMBI expression was observed in 148 (80.8%), and strong BAMBI expression was observed in 46% of the CRCs. Strong BAMBI expression was positively correlated with histological type, depth of invasion, lymph node metastases, and tumor node metastasis (TNM) stage (P < 0.05). Clear associations were found between BAMBI and β-catenin (P = 0.035) and p53 (P = 0.049) expression. In curatively resected CRC, 5-year recurrence-free survival was 51.9% (P = 0.037) for strong BAMBI expression compared to 79.8% for weak BAMBI expression. In the Cox’s multivariate analysis, lymph node metastases (RR 6.685; P < 0.001) and depth of invasion (RR 14.0; P = 0.013) were signifi cant indicators for recurrence, and strong BAMBI expression (RR 2.26; P = 0.057) tended to be signifi cant. CONCLUSION: BAMBI was linked to a potentially aggressive tumor phenotype and predicted tumor recurrence and cancer-related death in CRC. BAMBI expression might be applicable in the routine clinical setting of CRC. | Nozomi Togo Susumu Ohwada Shinji Sakurai Hiroyuki Toya Ichiro Sakamoto Tatsuya Yamada Tetsuhiro Nakano Ken Muroya Izumi Takeyoshi Takashi Nakajima Takashi Sekiya Yusuke Yamazumi Tsutomu Nakamura Tetsu Akiyama | 2008 | World Journal of Gastroenterology2008，14，31： | 3 |
| 5 | Internal structures and high-velocity frictional properties of Longmenshan fault zone at Shenxigou activated during the 2008 Wenchuan earthquake显示文摘This paper reports internal structures of a wide fault zone at Shenxigou,Dujiangyan,Sichuan province,China,and high-velocity frictional properties of the fault gouge collected near the coseismic slip zone during the 2008 Wenchuan earthquake.Vertical offset and horizontal displacement at the trench site were 2.8 m(NW side up)and 4.8 m(right-lateral),respectively.The fault zone formed in Triassic sandstone,siltstone,and shale about 500 m away from the Yingxiu-Beichuan fault,a major fault in the Longmenshan fault system.A trench survey across the coseismic fault,and observations of outcrops and drill cores down to a depth of 57 m revealed that the fault zone consists of fault gouge and fault breccia of about0.5 and 250–300 m in widths,respectively,and that the fault strikes N62°E and dips 68° to NW.Quaternary conglomerates were recovered beneath the fault in the drilling,so that the fault moved at least 55 m along the coseismic slip zone,experiencing about 18 events of similar sizes.The fault core is composed of grayish gouge(GG) and blackish gouge(BG) with very complex slip-zone structures.BG contains low-crystalline graphite of about 30 %.High-velocity friction experiments were conducted at normal stresses of 0.6–2.1 MPa and slip rates of 0.1–2.1 m/s.Both GG and BG exhibit dramatic slip weakening at constant high slip rates that can be described as an exponential decay from peak friction coefficient lpto steadystate friction coefficient lssover a slip-weakening distance Dc.Deformation of GG and BG is characterized by overlapped slip-zone structures and development of sharp slickenside surfaces,respectively.Comparison of our data with those reported for other outcrops indicates that the high-velocity frictional properties of the Longmenshan fault zones are quite uniform and the high-velocity weakening must have promoted dynamic rupture propagation during the Wenchuan earthquake. | Yu Wang Shengli Ma Toshihiko Shimamoto Lu Yao Jianye Chen Xiaosong Yang Honglin He Jiaxiang Dang Linfeng Hou Tetsuhiro Togo | 2014 | Earthquake Science2014，27，5： | 3 |
| 6 | Stick–slip behavior of Indian gabbro as studied using a NIED large-scale biaxial friction apparatus显示文摘This paper reports stick–slip behaviors of Indian gabbro as studied using a new large-scale biaxial friction apparatus, built in the National Research Institute for Earth Science and Disaster Prevention(NIED), Tsukuba, Japan. The apparatus consists of the existing shaking table as the shear-loading device up to 3,600 k N, the main frame for holding two large rectangular prismatic specimens with a sliding area of 0.75 m2 and for applying normal stresses rnup to 1.33 MPa, and a reaction force unit holding the stationary specimen to the ground. The shaking table can produce loading rates v up to 1.0 m/s,accelerations up to 9.4 m/s2, and displacements d up to0.44 m, using four servocontrolled actuators. We report results from eight preliminary experiments conducted with room humidity on the same gabbro specimens at v = 0.1–100 mm/s and rn= 0.66–1.33 MPa, and with d of about 0.39 m. The peak and steady-state friction coefficients were about 0.8 and 0.6, respectively, consistent with the Byerlee friction. The axial force drop or shearstress drop during an abrupt slip is linearly proportional to the amount of displacement, and the slope of this relationship determines the stiffness of the apparatus as1.15 9 108N/m or 153 MPa/m for the specimens we used.This low stiffness makes fault motion very unstable and the overshooting of shear stress to a negative value was recognized in some violent stick–slip events. An abrupt slip occurred in a constant rise time of 16–18 ms despite wide variation of the stress drop, and an average velocity during an abrupt slip is linearly proportional to the stress drop.The use of a large-scale shaking table has a great potential in increasing the slip rate and total displacement in biaxial friction experiments with large specimens. | Tetsuhiro Togo Toshihiko Shimamoto Futoshi Yamashita Eiichi Fukuyama Kazuo Mizoguchi Yumi Urata | 2015 | Earthquake Science2015，28，2： | 1 |
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