Preliminary study on active features of Fenghuang-shan-Tianshui fault, West Qinling north boundary fault zone since the late of Late Pleistocene

West Qinling north boundary fault zone (WQNBFZ) is a major NWW-striking fault in the east boundary of Tibetan Plateau, which is parallel to the Xianshuihe fault zone, Eastern Kunlun fault zone and Haiyuan fault zone. It is of mainly sinistral strike-slip. England and Molnar (1990) and WANG and MA (1998) proposed that these strike-slip faults divided the east part of Tibetan Plateau into elongate blocks, which slide successively towards the east, accompanied possibly by the clockwise rotation. What is more, the occurrence frequency of earthquakes with M 36.5 along WQNBFZ is also high, such as BC 47 Zhangxian M=6.8 earthquake, the 128 Gangu M=6.5 earth-quake, the 143 Gangu M=7 earthquake, the 734 Tianshui M=7 earthquake, the 1756 Wushan M=6.5 earthquake and the 1936 Kangle M=6.8 earthquake. However, compared with researches on Haiyuan fault zone, Xianshuihe fault zone and Longmenshan fault zone (Institute of Geology of State Seismological Bureau, Seismological Bureau of Ningxia Hui Autonomous Region, 1990; LI, 1993; DENG, et al, 1994; Burchfiel, et al, 1995), the study on WQNBFZ is still weak, although some researches have been done by KANG (1990) and TENG, et al (1991). Based on the field investigation and sample dating, the active features about the Fenghuangshan-Tianshui fault (FTF) of WQNBFZ are discussed in the paper.……

Heart Rate Variability, Standard of Measurement, Physiological Interpretation and Clinical Use in Mountain Marathon Runners during Sleep and after Acclimatization at 3480 m

Fluctuations in autonomic cardiovascular regulation during exposure to high altitude may increase the risk of heart attack during waking and sleep. This study compared heart rate variability (HVR) and its components during sleep at low altitude and after 30 - 41 hours of acclimatization at high altitude (3480 m) in five mountain marathon runners controlled for diet, drugs, light-dark cycle and jet lag. In comparison to sea level, RR-intervals during sleep at high altitude decreased significantly (P 0.001). The significant increase in sympathetic autonomic cardiovascular modulation at high altitude protects against excessive oxygen deprivation during sleep. Increases in R-R intervals can require longer periods of acclimatization at3480 m to mitigate the effects of altitude/hypoxia on sympathetic tone, thus reducing cardiovascular distress at rest during waking and sleep and probably before during and after athletic performance at altitude.

An example of earthquake nucleation of the strong continental earthquakes

Introduction The study on earthquake nucleation is widely concerned by seismologists in the world. The experimental and theoretical studies indicate that earthquakes should be preceded by quasi-static slip within a nucleation zone (Oh-naka, 1992; Dodge, Beroza, 1995; Dodge, et al, 1996; Ohnaka, Kuwahara, 1990; Yamashita, Ohnaka, 1991). The earthquake nucleation process means a transition from quasi-static to quasi-dynamic rupture process, and it itself is a short-term precursor. Immediate foreshocks are local dynamic instabilities that occur during the transition from the quasi-static to the quasi-dynamic nucleation of the dynamic instability (Ohnaka, 1992). According to the recent theoretical study, immediate foreshocks can be regarded as the localized fractures accompanied by the quasi-static nucleation process of a large earthquake (Shibazaki, Matsu'ura, 1995). Therefore, foreshocks could occur during the nucleation process. The nucleation of earthquakes can be illuminated through analyzing foreshock activity in detail. Detection of the nucleation process by means of a foreshock study is a potential tool for earthquake predic-tion. The nucleation process of Izu peninsula earthquake with M=7.0 on January 14, 1978 is revealed by Ohnaka with foreshock activities. It was observed that the nucleation zone indicated by foreshocks grew at a rate of 1～40 cm/s before reaching a diameter of 10 km. The depths of foreshocks do not change much more, keep within 10 km. Recently, Hurukawa have studied the nucleation process of Off-Etorofu earthquake with MW=7.9 on December 3, 1995. The results show distinctly the nucleation process before the main shock. In the nucleation process, rupture started at the deepest point of the foreshock area, and then propagated to the shallow depth with the apparent ve-locity of 5～20 cm/s (Hurukawa, 1998). Rastogi and Mandal (1998) studied the rupture nucleation process of five Koyna medium-sized main shocks using the time-space patterns of foreshocks. They found that the nucleation zone grew at a rate of 0.5～10 cm/s until it finally attained a diameter of about 10 km before the occurrence of the main shock and the fracture nucleated at shallow depths and gradually deepened, the main shock occurred at the deepest point of the nucleation zone, that is, at the depth of about 8～11 km. Foreshock distribution showed a good agreement with the preslip model of earthquake nucleation (Rastogi, Mandal, 1998).……