Two types of microseisms
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In general, microseisms are a nuisance.It is n9w quite widely agreed that microseisms are channel waves, similar in nature to the Lg and Rg waves.It is not at all unusual to observe microseisms which have traveled over distances of continental proportions.In order to determine the direction from which the microseisms come and to investigate in more detail the characteristics of microseismic disturbances, we established a tri-partite system on Mount Palomar.The array consisted of three stations, located at the vertices of a triangle, which was about 2,500 feet on a side.Two Benloft strain seismographs and one Bentoff vertical pendulum seismograph were installed in a strain vault at one location.One vertical pendulum seismograph was installed at a second location, and two horizontal and one vertical pendulum seismographs were installed at a third location.Portions of the records which were obtained on two consecutive days are included in Figure 1.The direction of approach can be calculated from the displacement between the peaks on the three verticals.These observations indicated that the waves practically always come from the coast.The direction of approach generally lies between north-northwest and south-southwest.The horizontal pendulum traces in record (a) are parallel.This indicates'that the horizontal motion is in a northeast-southwest direction and vice versa.Everything on record (a) points to a Rayleigh type motion.Shear waves predominate on record (b).The fact that the horizontal pendulums are opposed to each other indicates that the motion is in a northwest-southeast direction.The horizontal component of displacement is, therefore, perpendicular to the direction of propagation.The sum of strain components is practically zero, as it should be for a horizontally polarized shear wave.The vertical pendulums show some stoa1!motions.This is to be expected, since some Rayleigh type motion is always present.Both of these waves are character~ ized by six-second periods, but usually the Rayleigh type motion predominates.Among the many other types of microseisms which are observed are the twosecond microseisms with wavelengths between about one-third and one-half the wavelength of the six-second waves and practically the same velocity.These waves originate near the coast--probably on the continental shelf.it is generally believed that they are generated by turbulent air masses over the continental shelf.The horizontal pendulum and the horizontal strain seismographs show practically only the six-second waves and very little of the shorter waves.We were puzzled by the [act that here we had a wave which traveled with the Rayleigh wave velocity but possessed mainly a vertical component.Fortunately, Dr. Press could give us the probable solution.Drs.Keywords:
Microseism
Microseism
Swell
Seismogram
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Spatical position of microseismic source is one of the most important parameters in microseismic monitoring.Improving the accuracy of source location is an important content to study the microseismic monitoring technologies.A new microseismic location method on the basis of waveform was put forward,which could effectively avoid the locating error caused by speed in traditional methods and fully used seismic record data to rapidly and accurately locate the microseismic source.The new method was tested in Jinshandian Mine with existing microseismic monitoring system.Through blasting simulation of microseismic source,the feasibility of this method was proved.
Microseism
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Microseism
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Microseisms are ground vibrations caused largely by ocean gravity waves. Multiple spatially separate noise sources may be coincidentally active. A method for source separation and individual wavefield retrieval of microseisms using a single pair of seismic stations is introduced, and a method of back azimuth estimation assuming Rayleigh‐wave arrivals of microseisms is described. These methods are combined to separate and locate sources of microseisms in a synthetic model and then applied to field microseismic recordings from Ireland in the Northeast Atlantic. It is shown that source separation is an important step prior to location for both accurate microseism locations and microseisms wavefield studies.
Microseism
Rayleigh Wave
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The simulation experiment of the vehicle action on pavement was carried on. In the progress of the experiment, HZ-MS48 microseismic monitoring system was used to collect microseismic waves. And these microseismic signals were disposed and analyzed. It introduced the scheme and the process of the data collecting experiment. After that, several types of microseismic waveform were compared and discussed. Also shock waves for transmitting characteristic in pavement base were studied. At the same time, taking a typical microseismic event location as a case, the precision of microseismic event location was confirmed, which put forward a new way for monitoring traffic vehicles.
Microseism
Base (topology)
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Three series of simultaneous wave and microseism records are examined. They give a clear indication that bands of microseismic waves from different sources can be distinguished by submitting seismograph records to frequency analysis. The agreement between the results of analysis and the theoretical expectation from the prevailing meteorological conditions appears to justify the assumption that microseismic waves of different periods travel independently. Under the simple meteorological conditions that have been studied, each band of microseismic activity can be identified with a band of sea waves of twice its period. The existence of this two to one ratio between the period of waves and microseisms affords some confirmation of the theory that microseisms are produced in a region of interference between similar wave trains travelling in opposite directions either near the coast or in deep water.
Microseism
Seismometer
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在 Dagangshan 水力发出的电力车站的正确银行斜坡的挖掘的影响的体积，西南中国，实质上从 microseismic 监视，数字建模和象在 situ 观察一样的常规大小被决定。监视的 Microseismic 是为在岩石斜坡调查 microcrackings 的一种新申请技术。监视网络的 microseismic 系统地被用来监视由于斜坡和压力再分配以后由水坝被坝所围住的水引起了的岩石的连续挖掘卸掉松驰的岩石群众，并且识别并且描出潜在的滑动区域自从 2010 年 5 月。地震来源地点的一个重要数据库是可得到的。microseismic 事件的分析显示出特别速度空间的分布。地震事件主要发生在 1180 m 举起的在上游的斜坡附近，特别集中于差错 XL316-1 的挂的墙。如此的现象被用 RFPA-SRM 代码(现实主义的失败进程分析力量减小方法) 的数字建模解释。由把 microseismic 活动和数字模拟的结果与作比较在地点，观察和常规大小导致，强壮的关联能在工作区域在地震来源地点和导致挖掘的压力分发之间被获得。岩石斜坡的影响的体积因此是坚定的。工程惯例证明监视的 microseismic 能精确地诊断大小，紧张和象差错和卸掉的地区那样的构造活动的联系速度空间的特征。把地震监视与数字建模相结合的综合技术，以及在地点观察并且常规调查，从不同观点在正确银行斜坡导致在 microseismic 活动和压力地之间的内部效果和关系的更好的理解。
Microseism
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In general, microseisms are a nuisance.It is n9w quite widely agreed that microseisms are channel waves, similar in nature to the Lg and Rg waves.It is not at all unusual to observe microseisms which have traveled over distances of continental proportions.In order to determine the direction from which the microseisms come and to investigate in more detail the characteristics of microseismic disturbances, we established a tri-partite system on Mount Palomar.The array consisted of three stations, located at the vertices of a triangle, which was about 2,500 feet on a side.Two Benloft strain seismographs and one Bentoff vertical pendulum seismograph were installed in a strain vault at one location.One vertical pendulum seismograph was installed at a second location, and two horizontal and one vertical pendulum seismographs were installed at a third location.Portions of the records which were obtained on two consecutive days are included in Figure 1.The direction of approach can be calculated from the displacement between the peaks on the three verticals.These observations indicated that the waves practically always come from the coast.The direction of approach generally lies between north-northwest and south-southwest.The horizontal pendulum traces in record (a) are parallel.This indicates'that the horizontal motion is in a northeast-southwest direction and vice versa.Everything on record (a) points to a Rayleigh type motion.Shear waves predominate on record (b).The fact that the horizontal pendulums are opposed to each other indicates that the motion is in a northwest-southeast direction.The horizontal component of displacement is, therefore, perpendicular to the direction of propagation.The sum of strain components is practically zero, as it should be for a horizontally polarized shear wave.The vertical pendulums show some stoa1!motions.This is to be expected, since some Rayleigh type motion is always present.Both of these waves are character~ ized by six-second periods, but usually the Rayleigh type motion predominates.Among the many other types of microseisms which are observed are the twosecond microseisms with wavelengths between about one-third and one-half the wavelength of the six-second waves and practically the same velocity.These waves originate near the coast--probably on the continental shelf.it is generally believed that they are generated by turbulent air masses over the continental shelf.The horizontal pendulum and the horizontal strain seismographs show practically only the six-second waves and very little of the shorter waves.We were puzzled by the [act that here we had a wave which traveled with the Rayleigh wave velocity but possessed mainly a vertical component.Fortunately, Dr. Press could give us the probable solution.Drs.
Microseism
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In the sublevel caving longwall face #3201 of Chaoyang Coal Mine,an abnormal phenomenon is detected that the amplitude of detector receiving microseismic wave earlier is bigger than the one receiving microseismic wave later by using high-precision microseismic monitoring system and then a strong underground vibration is felt.In response to this anomaly,the layout of high-precision microseismic monitoring system and system calibration is introduced.Through the abnormal waveform data analysis and preliminary positioning,that the results of microseismic positioning do not meet the requirements of positioning accuracy is discovered,thus negating the basic assumptions of considering the record of the microseismic data as one source to locate.On this basis,a hypothesis is put forward,that is,the mechanism of microseim-induced rock burst is the pattern of the vibration wave of the inital microseismic source inducing another microseismic source by the vibrational failure of s-wave,and the hypothesis is proved strictly.Considering of underground pressure and stratum control and the results of long-term microseismic monitoring,the location of the induced microseismic source is found exactly under the high-stress area of mining-induced stress field and tectonic stress field,which is further proof of the above hypothesis and makes it clear that the induced microseismic source is located in the high-stress areas under the influence of coupling factors.
Microseism
Rock burst
Stress field
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