Based on the body strain record of Tiantanghe station from 2008 to 2014,we make a statistical analysis of the relationship between the maximum amplitude of the body strain record and the surface-wave magnitude,epicenter distance of the earthquakes,which occurred in the Chinese mainland and its surrounding areas with MS≥6. 0 and the rest of the world with MS≥7. 0. According to statistical results,we propose a statistical formula between the surface-wave magnitude of earthquake and the maximum amplitude of the body strain record,the epicenter distance: M_S~*= 0. 37 ln A_max+ 0. 57 ln D + 0. 07. We can also derive a theoretical estimation formula for the maximum amplitude: A_max=e~(2. 7(M_S~*-0. 07))D~(-1. 54). This demonstrates that the maximum amplitude of the body strain record increases exponentially with the increase of the surface-wave magnitude, and decreases with the increase of the epicenter distance,and shows a negative correlation with their product. We further discuss the necessity of adding instruments with high frequency sampling to earthquake monitoring, and dicuss the prospects for precise earthquake prediction in future. 相似文献
The earthquake stress-drop values of two sequences were accurately calculated after taking away the effects due to regional earthquake anelastic attenuation and station site response, using waveform data and seismic phase data of sequences of the Jinggu MS6.6, and Ludian MS6.5 earthquakes in Yunnan. These results show that the stress drop with magnitude increases within the scope of this study of magnitude. After eliminating the influence of the magnitude, the average value of stress-drop in the Jinggu sequence is higher than that of the Ludian sequence at the same magnitude range. This may be related to the stress state in different regions. In terms of the changes of time and space of stress-drop, before MS5.8 strong aftershock, the stress-drop is "slowing down-turning up-keeping a high value" after the mainshock, meanwhile, almost all of the abnormally high stress drop value is distributed around the MS5.8 strong aftershock, showing that the stress environment in the region was increasing after the mainshock. And after the MS5.9 strong aftershock, stress-drop rapidly declines to a relatively stable state, meanwhile, the high value of stress-drop is distributed around the strong aftershock, showing that the regional tectonic stress gets more fully release, its stress environment begins to rapidly decrease. For the Ludian sequence without a strong aftershock occurring, the average value of stress drop is lower than that of the Jinggu earthquake sequence at the same magnitude range, while at the same time, the stress-drop of the aftershock sequence almost hasn''t changed much. In the time after the mainshock, combined with the release characteristics of the main energy, the stress in the region is excessively released, the subsequent stress in the region gradually returns to normal. This may be the reason why the activity of Ludian aftershocks significantly was weaker and subsequently there were no strong aftershocks occurred. 相似文献
Persistent economic growth in Chinese southwestern Yunnan Province is setting aquatic ecosystems in its plateau lakes under enormous pressure. While several different systems have previously been used to study these lakes, no existing methodology adequately measures both the chemical and biotic parameters of these water bodies. Here, we present a novel Biotic Monitoring Yunnan Lakes (BMYL) index that provides a general assessment tool for ecological deterioration that is caused by organic pollution. Principal Component Analysis is used to analyze the occurrence of families of macroinvertebrates and chemical properties of the lakes. In brief, families of macroinvertebrates were given a score from 10 to 1 based on sensitivity to organic enrichment and eutrophication. Sampling at each lake yielded an Average Score per Lake (ASPL) which is calculated by dividing the total BMYL by the total number of scoring families. High ASPL values characterize a biologically intact lake containing relatively large numbers of high scoring taxa, while lower ASPL values denote a polluted lake that does not support many high scoring taxa. The results of the BMYL show a notably more accurate characterization of the long-term health of concerned aquatic ecosystems than studies that use abundance levels of species or a simple analysis of chemical parameter. 相似文献
The composition and concentration of dissolved free amino acid (DFAA) of seawater samples collected in May 2016 from the surface to the hadal zone of the northern region of the Yap Trench were analyzed by pre-column derivatization of o-phthalaldehyde. Results show that the average concentration of DFAA in the study area was 0.47±0.36 µmol/L. In different sampling stations, the concentrations of DFAA with water depth showed complex variation patterns. At the sediment-seawater interface, the concentrations of DFAA in the western side of the trench were obviously higher than that in its eastern side. In the study area, there were no significant correlations between the concentrations of DFAA and the environmental parameters such as concentrations of chlorophyll a (Chl a), dissolved oxygen (DO), pH, and dissolved inorganic nitrogen (DIN), indicating that the concentrations of DFAA in seawater of the trench are affected by many factors, such as photosynthesis, respiration, temperature, pressure, illumination, and circulation. The dominant DFAA are similar in different water layers of sampling stations, including aspartic acid (Asp), glutamic acid (Glu), glycine (Gly), and serine (Ser). The composition of different amino acids, and the relative abundance of acidic, basic, and neutral amino acids might be related to the sources and consumption of various amino acids. Nine pairs of amino acids in the DFAA showed significantly positive relationship by correlation matrix analysis, suggesting that they might share similar biogeochemical processes. The degradation index (DI) of the DFAA in seawater of the Yap Trench could reflect the degradation, source, and freshness of DFAA in the trench to some extents. This is a preliminary study of amino acids from sea surface to hadal zone in the ocean, more works shall be done in different trenches to reveal their biogeochemical characteristics in extreme marine environments.
After the 2015 MS8.1 Nepal earthquake, a strong and moderate seismicity belt has formed in Tibet gradually spreading along the northeast direction. In this paper, we attempt to summarize the features and investigate the primary mechanism of this behavior of seismic activity, using a 2-D finite element numerical model with tectonic dynamic settings and GPS horizontal displacements as the constraints. In addition, compared with the NE-trending seismicity belt triggered by the 1996 Xiatongmoin earthquake, we discuss the future earthquake hazard in and around Tibet. Our results show that:the NE-directed seismicity belt is the response of enhanced loading on the anisotropic Qinghai-Tibetan plateau from the Indian plate and earthquake thrusting. Also, this possibly implies that a forthcoming strong earthquake may fill in the gaps in the NE-directed seismicity belt or enhance the seismic hazard in the eastern (the north-south seismic zone) and western (Tianshan tectonic region) parts near the NE-directed belt. 相似文献