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Pressure induced by the interaction of water waves with nearly equal frequencies and nearly opposite directions

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Theoretical & Applied Mechanics Letters 2017年第3期7卷 138-144页

作者： L. Pellet P. Christodoulides S. Donne C.J. Bean F. Dias Ecole Centrale Marseille Marseille France Faculty of Engineering and Technology Cyprus University of Technology Limassol Cyprus School of Earth Sciences University College Dublin Belfield Dublin 4 Ireland School of Cosmic Physics Dublin lnstitute for Advanced Studies Dublin 2 Ireland School of Mathematics and Statistics University College Dublin Beheld Dublin 4 Ireland

We present second-order expressions for the free-surface elevation, velocity potential and pressure resulting from the interaction of surface waves in water of arbitrary depth. When the surface waves have nearly equal frequencies and nearly opposite directions, a second-order pressure can be felt all the way to the sea bottom. There are at least two areas of applications： reflective structures and microseisms. microseisms generated by water waves in the ocean are small vibrations of the ground resulting from pressure oscillations associated with the coupling of ocean surface gravity waves and the sea floor. They are recorded on land-based seismic stations throughout the world and they are divided into primary and secondary types, as a function of spectral content. Secondary microseisms are generated by the interaction of surface waves with nearly equal frequencies and nearly opposite directions. The efficiency of microseism generation thus depends in part on ocean wave frequency and direction. Based on the second-order expressions for the dynamic pressure, a simple theoretical analysis that quantifies the degree of nearness in amplitude, frequency, and incidence angle, which must be reached to observe the phenomenon, is presented.

关键词： Ocean wave-wave interaction Pressure microseisms

Noise Suppression for Micro-seismic on Gas Shale

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Acta Geologica Sinica(English Edition) 2015年第A1期89卷 367-368页

作者： XIE Qingming LI Dahua CHENG Lijun WANG Fei HUANG Zhenhua WANG Dayuan Key Laboratory of Shale Gas Exploration Ministry of Land and Resources Chongqing Institute of Geology and MineralResources Chongqing 400042 Chongqing Engineering Research Center for Shale Gas Resource & Exploration Chongqing Institute of Geology andMineral Resources Chongqing 400042 Chongqing Shale Gas Research Centre of State Key Laboratory of Petroleum Resource and Prospecting ChongqingInstitute of Geology and Mineral Resources Chongqing 400042

1 Introduction Gas shale reservoirs have the characteristics with low porosity and permeability, no air-water interface, self- storage, a large area of continuous accumulation, etc. With monitoring the hydraulic fracturing of gas shale reservoir, some key results, fracture direction, distribution, and other geometric features （crack length, width and height）, etc., would be forecasted with micro-seismic data produced by rock fracture. It provides real-time, accurate information for reservoir stimulation.

关键词： GAS reservoirs OIL shales ROCK noise microseisms HYDRAULIC structures SHALE gas ALGORITHMS

A Preliminary Study on the Phenomenon of Microseismic Fluctuations before Impending Strong Earthquake

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Earthquake Research in China 2019年第3期33卷 367-390页

作者： YANG Liming HAO Zhen WANG Jianjun ZHANG Shuzhen YAO Jiajun DONG Lei Lanzhou Institute of Seismology CEALanzhou 730000China Qinghai Earthquake Agency Xining 810001China Geophysical Exploration Center CEAZhengzhou 450002China Chongqing Earthquake Agency Chongqing 401147China

Based on repeated comparison studies of broadband digital seismic records before the Wenchuan MS8. 0,Yushu MS7. 1 and Qingchuan MS5. 4 earthquakes,the possible microseismic fluctuations before impending earthquakes were preliminarily identified. In order to verify and test this phenomenon,a real-time tracking technical system was established by using continuous waveform records of more than 200 wide-band digital seismic stations in regional networks such as Gansu,Qinghai,Sichuan,Yunnan and *** real-time tracking and dynamic monitoring of 24 earthquakes with M≥5. 0 occurring in the Qinghai-Tibetan block during the period of 2012-2014 and the observations of stations in some non-seismic areas,the reproducibility and objectivity of the impending earthquake phenomenon were verified. The main characteristics of the microseismic fluctuation phenomena immediately preceding the strong earthquakes are as follows:(1)the spectrum range is wider,the dominant frequency is 11-16 Hz,and the spectrum shape is more regular;(2)it appears 6-24 days before the earthquake,averaging about 15 days;(3)it is possible to be recorded by the stations within the epicenter distance of 50 km,and the stations with the epicenter distance of more than 50 km generally cannot record it;(4)this phenomenon is directional,i. e. the direction in which the activity degree,N-value,varies significantly may be related to the location of the seismic source,the seismogenic fault and the distribution of aftershocks of the strong earthquake. The preliminary study shows that the impending-earthquakes microseismic phenomena may be related to the pre-activity,micro-vibration and micro-rupture in the source region in the imminent stage,or the microactivity and micro-rupture associated with the active tectonics.

关键词： Impending microseisms Dominant frequency 11-16Hz Space-time characteristics Pre-activity of source area

Anomalous tremor before 2008 Ms8.0 Wenchuan earthquake: a review

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Geodesy and Geodynamics 2011年第3期2卷 56-60页

作者： Hao Xiaoguang Hu Xiaogang Tian Lianghui Key Laboratory of Dynamical Geodesy Institute of Geodesy and Geophysics Chinese Academy of Science Wuhan 430077 China

In this paper we give a review of several previously published papers on anomalous tremors observed before the 2008 Ms8.0 Weuchuan earthquake. Based on the observed time and frequency shifts between coastal and inland stations, we discussed some methods to distinguish different kinds of microseisms, and speculated that a pre-earthquake typhoon might have caused a ＂mainland-originated microseism＂ which in turn trig- gered the earthquake.

关键词： Ms8.0 Wenchuan earthquake anomalous tremors before earthquake review microseisms ty-phoon