The Debao MS4.8 earthquake occurred in western Guangxi on August 5,2021,near where the Jingxi MS5.2 earthquake occurred in 2019.To study the increasing seismicity in western Guangxi,it is necessary to determine whethe...The Debao MS4.8 earthquake occurred in western Guangxi on August 5,2021,near where the Jingxi MS5.2 earthquake occurred in 2019.To study the increasing seismicity in western Guangxi,it is necessary to determine whether there was an anomaly related to the earthquake source near the Pingxiang gravity station,which is located approximately 100 km from the epicenter of the Debao MS4.8 earthquake.In this study,the R-value scoring method was used to analyze the anomaly and evaluate the prediction efficiency of the double frequency(DF)micro-seismic signal vertical displacement(referred to as vertical displacement,VD)and the absolute value of monthly extreme rate(referred to as the monthly rate).Results show that earthquakes larger than MS4.0 in the 350 km range from the Pingxiang station tend to coincide with yearly typhoons,and the VD of micro-seismic signals correspondingly changes from low to high.The Debao MS4.8 earthquake occurred during a gradual VD increase from 0.05×10^(-6)to 0.10×10^(-6)m.When discussing the relationships among R,the rate threshold,and the effective duration of prediction,the rate threshold of the micro-seismic signal converges from 0.00039×10^(-6)to 0.00031×10^(-6)m/month,the effective duration of prediction is approximately 6-10 months,and R also converges from 0.29 to 0.31.By comparing the results of three gPhone gravity stations in Guangxi,we found that the increase of short-term VD before the Debao earthquake was related to the enhancement of the DF micro-seismic signal excited by the typhoon.When the typhoon track was perpendicular to the coastline of China,the possibility of an earthquake occurring was increased.This study provides evidence and reference for the future occurrence period of earthquakes above MS4.0 in western Guangxi.展开更多
A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed...A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of -2 km. The high-resolution P-velocity model revealed interesting structures in the seismogenic layer: (1) The Guanxian-Anxian fault, Yingxiu-Beichuan fault and Wenchuan-Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; (2) The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least -10 km from the surface; (3) A sharp lateral velocity variation beneath the Wenchuan-Maoxian fault may indicate that the Pengguan massif's western boundary and/or the Wenchuan-Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu-Beichuan and Guanxian-Anxian faults, and vertical Wenchuan-Maoxian fault; (4) Vicinity along the Yingxiu- Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; (5) Two blocks of low-velocity anomaly are respectively imaged in the hanging wall and foot wall of the Guanxian-Anxian fault with a -7 km offset with -5 km vertical component.展开更多
Micro-seismic monitoring is one of the most critical technologies that guide hydraulic fracturing in hot dry rock resource development. Micro-seismic monitoring requires high precision detection of micro-seismic event...Micro-seismic monitoring is one of the most critical technologies that guide hydraulic fracturing in hot dry rock resource development. Micro-seismic monitoring requires high precision detection of micro-seismic events with a low signal-to-noise ratio. Because of this requirement, we propose a recurrent neural network model named gated recurrent unit and support vector machine(GRU;VM). The proposed model ensures high accuracy while reducing the parameter number and hardware requirement in the training process. Since micro-seismic events in hot dry rock produce large wave amplitudes and strong vibrations, it is difficult to reverse the onset of each individual event. In this study, we utilize a support vector machine(SVM) as a classifier to improve the micro-seismic event detection accuracy. To validate the methodology, we compare the simulation results of the short-term-average to the long-term-average(STA/LTA) method with GRU;VM method by using hot dry rock micro-seismic event data in Qinghai Province, China. Our proposed method has an accuracy of about 95% for identifying micro-seismic events with low signal-to-noise ratios. By ignoring smaller micro-seismic events, the detection procedure can be processed more efficiently, which is able to provide a real-time observation on the types of hydraulic fracturing in the reservoirs.展开更多
Micro-seismic phenomena, occurring when rock masses are subjected to forces and failures, allow the determination of their unstable states and failure zones by analyzing micro-seismic signals. We first present the pri...Micro-seismic phenomena, occurring when rock masses are subjected to forces and failures, allow the determination of their unstable states and failure zones by analyzing micro-seismic signals. We first present the principles of micro-seismic monitoring and location, as well as an underground explosion-proof micro-seismic monitoring system. Given a practical engineering application, we describe the application of micro-seismic monitoring technology in determining the height of a "two-zone" overburden, i.e., a caving zone and a fracture zone, the width of a coal-pillar section and the depth of failure of a floor. The workfaces monitored accomplished safe and highly efficient mining based on our micro-seismic monitoring results and provide direct proof of the reliability and validity of micro-seismic monitoring technology.展开更多
Blasting and breaking of hard roof are main inducing causes of rock bursts in coal mines with danger of rock burst,and it is important to find out the frequency spectrum distribution laws of these dynamic stress waves...Blasting and breaking of hard roof are main inducing causes of rock bursts in coal mines with danger of rock burst,and it is important to find out the frequency spectrum distribution laws of these dynamic stress waves and rock burst waves for researching the mechanism of rock burst.In this paper,Fourier transform as a micro-seismic signal conversion method of amplitude-time character to amplitude-frequency character is used to analyze the frequency spectrum characters of micro-seismic signal of blasting,hard roof breaking and rock bursts induced by the dynamic disturbance in order to find out the difference and relativity of different signals.The results indicate that blasting and breaking of hard roof are high frequency signals,and the peak values of dominant frequency of the signals are single.However,the results indicate that the rock bursts induced by the dynamic disturbance are low frequency signals,and there are two obvious peak values in the amplitude-frequency curve witch shows that the signals of rock bursts are superposition of low frequency signals and high frequency signals.The research conclusions prove that dynamic disturbance is necessary condition for rock bursts,and the conclusions provide a new way to research the mechanism of rock bursts.展开更多
A neural network is applied to high-quality 3-D seismic data during micro-seismic facies analysis to per- form the waveform analysis and training on single reflection events. Modeled seismic channels are estab- lished...A neural network is applied to high-quality 3-D seismic data during micro-seismic facies analysis to per- form the waveform analysis and training on single reflection events. Modeled seismic channels are estab- lished and the real seismic channels are classified. Thus, a distribution of micro-seismic facies having a high precision over a flat surface was acquired. This method applied to existing geological data allows the distribution of areas rich in coal bed methane to be clearly defined. A distribution map of the micro-seismic facies in the research area is shown. The data accord well with measured methane con- tents, indicating that the analysis using micro-seismic facies is reliable and effective. This method could be applied to coal bed methane exploration and is of great importance to future exploration work and to an increase in the drilling success rate.展开更多
An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to...An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to three nearest monitoring sensors in a sensor's array arrangement were the same. Since the defined objective function does not require pre-measurement of the stress wave propagation velocity in the field, errors from the velocity measurement can be avoided in comparison to three traditional velocity models. By analyzing 24 different cases, the proposed multidirectional velocity model iterated by the Simplex method is found to be the best option no matter the source is within the region of the sensor's array or not. The proposed model and the adopted iterative algorithm are verified by field data and it is concluded that it can significantly reduce the error of the estimated source location.展开更多
In this study,differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time–frequency analysis.The duration of t...In this study,differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time–frequency analysis.The duration of the mine shock is short while the coal and gas outburst lasts longer.The outburst consists of three stages:the pre-shock,secondary shock and main shock stage,respectively.The velocity amplitude of the mine shock is between 10^(-)5and 10^(-3)m/s,which is higher than that of the outburst with the same energy level.In addition,in both cases,the correlation between the velocity amplitude and energy is positive while the correlation between the signal frequency band distribution and energy is negative.The signal frequency band of the high energy mine shock is distributed between 0 and 50 Hz,and the low energy mine shock is between 50 and 100 Hz.The fractal characteristics of mine shocks were studied based on a fractal theory.The box dimensions of high energy mine shocks are lower than the low energy ones,however,the box dimensions of outbursts are higher than that of mine shocks with the same energy level.The higher box dimensions indicate more dangerous dynamic events.展开更多
Deduced the propagation rule of longitudinal and transverse wave.On the basis.of this,propagation rules in attenuated visco-eiastic media and Varied Lame coefficientwere put forward as well.The subsequent numerical an...Deduced the propagation rule of longitudinal and transverse wave.On the basis.of this,propagation rules in attenuated visco-eiastic media and Varied Lame coefficientwere put forward as well.The subsequent numerical analysis found that in a small scopelongitudinal and transverse wave could be considered as homogeneously propagatingwhen faultages and joints were not taken into account.The existence of lane hindered thewave's propagation,and it made the velocity gradient change in a locat vicinity area.Therefore velocity varied in different direction.展开更多
In this paper,a new 3D visualization technical method was developed for hydraulic fractures using micro-seismic monitoring.This technical method consists of four steps:i.interpret the geologic hydraulic fracture model...In this paper,a new 3D visualization technical method was developed for hydraulic fractures using micro-seismic monitoring.This technical method consists of four steps:i.interpret the geologic hydraulic fracture model based on seismic source location data from micro-seismic monitoring;ii.develop a hydraulic fracture indication model,relying on the 3D spatial freeze-frame of micro-seismic monitoring sources from hydraulic fracturing;iii.construct a hydraulic fracture density model using the intensity from the micro-seismic monitoring;and iv.implement a 3D visualization of the hydraulic fractures,relying on the spatial constraints of the density model,the hydraulic fracture indication model,and the properties of the hydraulic fractures.This proposed technical method was used to produce 3D visualizations of the hydraulic fractures in well X in the Jiao reservoir,China,and the 3D visualizations of the distribution,development,extent and cutting relationships of hydraulic fractures were successfully realized.The results show that this technical method can be used as a practical and reliable approach to characterize hydraulic fractures.展开更多
基金supported by grants from the Seismological Science and Technology Spark Program of China Seismological Bureau(grant number XH23026C)the National Natural Science Foundation of China(grant number41204058)。
文摘The Debao MS4.8 earthquake occurred in western Guangxi on August 5,2021,near where the Jingxi MS5.2 earthquake occurred in 2019.To study the increasing seismicity in western Guangxi,it is necessary to determine whether there was an anomaly related to the earthquake source near the Pingxiang gravity station,which is located approximately 100 km from the epicenter of the Debao MS4.8 earthquake.In this study,the R-value scoring method was used to analyze the anomaly and evaluate the prediction efficiency of the double frequency(DF)micro-seismic signal vertical displacement(referred to as vertical displacement,VD)and the absolute value of monthly extreme rate(referred to as the monthly rate).Results show that earthquakes larger than MS4.0 in the 350 km range from the Pingxiang station tend to coincide with yearly typhoons,and the VD of micro-seismic signals correspondingly changes from low to high.The Debao MS4.8 earthquake occurred during a gradual VD increase from 0.05×10^(-6)to 0.10×10^(-6)m.When discussing the relationships among R,the rate threshold,and the effective duration of prediction,the rate threshold of the micro-seismic signal converges from 0.00039×10^(-6)to 0.00031×10^(-6)m/month,the effective duration of prediction is approximately 6-10 months,and R also converges from 0.29 to 0.31.By comparing the results of three gPhone gravity stations in Guangxi,we found that the increase of short-term VD before the Debao earthquake was related to the enhancement of the DF micro-seismic signal excited by the typhoon.When the typhoon track was perpendicular to the coastline of China,the possibility of an earthquake occurring was increased.This study provides evidence and reference for the future occurrence period of earthquakes above MS4.0 in western Guangxi.
基金the Basic Research Foundation of the Institute of Geomechanics,CAGS(grant DZLXJK200707)Natural Science Foundation of China grant 40674058)
文摘A three-dimensional local-scale P-velocity model down to 25 km depth around the main shock epicenter region was constructed using 83821 event-to-receiver seismic rays from 5856 aftershocks recorded by a newly deployed temporary seismic network. Checkerboard tests show that our tomographic model has lateral and vertical resolution of -2 km. The high-resolution P-velocity model revealed interesting structures in the seismogenic layer: (1) The Guanxian-Anxian fault, Yingxiu-Beichuan fault and Wenchuan-Maoxian fault of the Longmen Shan fault zone are well delineated by sharp upper crustal velocity changes; (2) The Pengguan massif has generally higher velocity than its surrounding areas, and may extend down to at least -10 km from the surface; (3) A sharp lateral velocity variation beneath the Wenchuan-Maoxian fault may indicate that the Pengguan massif's western boundary and/or the Wenchuan-Maoxian fault is vertical, and the hypocenter of the Wenchuan earthquake possibly located at the conjunction point of the NW dipping Yingxiu-Beichuan and Guanxian-Anxian faults, and vertical Wenchuan-Maoxian fault; (4) Vicinity along the Yingxiu- Beichuan fault is characterized by very low velocity and low seismicity at shallow depths, possibly due to high content of porosity and fractures; (5) Two blocks of low-velocity anomaly are respectively imaged in the hanging wall and foot wall of the Guanxian-Anxian fault with a -7 km offset with -5 km vertical component.
基金supported by National Key R&D Program of China(Grant No.2018YFB1501803,2019YFC1804805-4)China Geological Survey Project(Grant No.DD2019135)。
文摘Micro-seismic monitoring is one of the most critical technologies that guide hydraulic fracturing in hot dry rock resource development. Micro-seismic monitoring requires high precision detection of micro-seismic events with a low signal-to-noise ratio. Because of this requirement, we propose a recurrent neural network model named gated recurrent unit and support vector machine(GRU;VM). The proposed model ensures high accuracy while reducing the parameter number and hardware requirement in the training process. Since micro-seismic events in hot dry rock produce large wave amplitudes and strong vibrations, it is difficult to reverse the onset of each individual event. In this study, we utilize a support vector machine(SVM) as a classifier to improve the micro-seismic event detection accuracy. To validate the methodology, we compare the simulation results of the short-term-average to the long-term-average(STA/LTA) method with GRU;VM method by using hot dry rock micro-seismic event data in Qinghai Province, China. Our proposed method has an accuracy of about 95% for identifying micro-seismic events with low signal-to-noise ratios. By ignoring smaller micro-seismic events, the detection procedure can be processed more efficiently, which is able to provide a real-time observation on the types of hydraulic fracturing in the reservoirs.
基金supported by the National Basic Research Program of China (No. 2010CB226805)the National Natural Science Foundation of China (No. 50874103)+1 种基金the State Laboratory Fund (No. SKLGDUEK0905)the Talent Introduction Fund of Anhui University of Science & Technology
文摘Micro-seismic phenomena, occurring when rock masses are subjected to forces and failures, allow the determination of their unstable states and failure zones by analyzing micro-seismic signals. We first present the principles of micro-seismic monitoring and location, as well as an underground explosion-proof micro-seismic monitoring system. Given a practical engineering application, we describe the application of micro-seismic monitoring technology in determining the height of a "two-zone" overburden, i.e., a caving zone and a fracture zone, the width of a coal-pillar section and the depth of failure of a floor. The workfaces monitored accomplished safe and highly efficient mining based on our micro-seismic monitoring results and provide direct proof of the reliability and validity of micro-seismic monitoring technology.
基金supported by the National Basic Research Program ofChina(No.2010CB202210)the National Natural Science Foundation of China(No.50874103)+1 种基金the Natural Science Foundation of Jiangsu Province(No.KB2008135)as well as by the Qinglan Project of Jiangsu Province
基金the National Basic Research Program of China (Nos.2005 CB221504 and 2010CB226805)the Research Fund of the State Key Laboratory of Coal Resources and Mine Safety,CUMT (No.09KF08)the Foundation of the Henan Educational Committee (No.2010 A440003)
文摘Blasting and breaking of hard roof are main inducing causes of rock bursts in coal mines with danger of rock burst,and it is important to find out the frequency spectrum distribution laws of these dynamic stress waves and rock burst waves for researching the mechanism of rock burst.In this paper,Fourier transform as a micro-seismic signal conversion method of amplitude-time character to amplitude-frequency character is used to analyze the frequency spectrum characters of micro-seismic signal of blasting,hard roof breaking and rock bursts induced by the dynamic disturbance in order to find out the difference and relativity of different signals.The results indicate that blasting and breaking of hard roof are high frequency signals,and the peak values of dominant frequency of the signals are single.However,the results indicate that the rock bursts induced by the dynamic disturbance are low frequency signals,and there are two obvious peak values in the amplitude-frequency curve witch shows that the signals of rock bursts are superposition of low frequency signals and high frequency signals.The research conclusions prove that dynamic disturbance is necessary condition for rock bursts,and the conclusions provide a new way to research the mechanism of rock bursts.
基金supported financially by the National Key Project(No. 2008ZX05035-005-003)the National Basic Research Program of China (No. 2009CB219603)
文摘A neural network is applied to high-quality 3-D seismic data during micro-seismic facies analysis to per- form the waveform analysis and training on single reflection events. Modeled seismic channels are estab- lished and the real seismic channels are classified. Thus, a distribution of micro-seismic facies having a high precision over a flat surface was acquired. This method applied to existing geological data allows the distribution of areas rich in coal bed methane to be clearly defined. A distribution map of the micro-seismic facies in the research area is shown. The data accord well with measured methane con- tents, indicating that the analysis using micro-seismic facies is reliable and effective. This method could be applied to coal bed methane exploration and is of great importance to future exploration work and to an increase in the drilling success rate.
基金Project(IRT0950)supported by the Cheung Kong Scholars and the Development Plan of Innovative Team,ChinaProject supported by China Scholarship Council
文摘An improved multidirectional velocity model was proposed for more accurately locating micro-seismic events in rock engineering. It was assumed that the stress wave propagation velocities from a micro-seismic source to three nearest monitoring sensors in a sensor's array arrangement were the same. Since the defined objective function does not require pre-measurement of the stress wave propagation velocity in the field, errors from the velocity measurement can be avoided in comparison to three traditional velocity models. By analyzing 24 different cases, the proposed multidirectional velocity model iterated by the Simplex method is found to be the best option no matter the source is within the region of the sensor's array or not. The proposed model and the adopted iterative algorithm are verified by field data and it is concluded that it can significantly reduce the error of the estimated source location.
基金the Key Research Development Program of Jiangsu Province (No.BE2015040)the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Graduate Student Research Innovation Project of Jiangsu Province (No.KYLX_1403)
文摘In this study,differences of signal characteristics between mine shocks and coal and gas outbursts in coal mines were examined with the micro-seismic monitoring technique and time–frequency analysis.The duration of the mine shock is short while the coal and gas outburst lasts longer.The outburst consists of three stages:the pre-shock,secondary shock and main shock stage,respectively.The velocity amplitude of the mine shock is between 10^(-)5and 10^(-3)m/s,which is higher than that of the outburst with the same energy level.In addition,in both cases,the correlation between the velocity amplitude and energy is positive while the correlation between the signal frequency band distribution and energy is negative.The signal frequency band of the high energy mine shock is distributed between 0 and 50 Hz,and the low energy mine shock is between 50 and 100 Hz.The fractal characteristics of mine shocks were studied based on a fractal theory.The box dimensions of high energy mine shocks are lower than the low energy ones,however,the box dimensions of outbursts are higher than that of mine shocks with the same energy level.The higher box dimensions indicate more dangerous dynamic events.
基金Supported by International Important Cooperation Project of National Natural Science Foundation of China(50320120001).
文摘Deduced the propagation rule of longitudinal and transverse wave.On the basis.of this,propagation rules in attenuated visco-eiastic media and Varied Lame coefficientwere put forward as well.The subsequent numerical analysis found that in a small scopelongitudinal and transverse wave could be considered as homogeneously propagatingwhen faultages and joints were not taken into account.The existence of lane hindered thewave's propagation,and it made the velocity gradient change in a locat vicinity area.Therefore velocity varied in different direction.
基金We are grateful for the support of the National Major Basic Research Development Program of China(2014CB239205)the Sichuan Science and Technology Program(Grant No.2021YFQ0049)the sub-project of the National Science and Technology Major Project(Grant No.2017ZX05035003).
文摘In this paper,a new 3D visualization technical method was developed for hydraulic fractures using micro-seismic monitoring.This technical method consists of four steps:i.interpret the geologic hydraulic fracture model based on seismic source location data from micro-seismic monitoring;ii.develop a hydraulic fracture indication model,relying on the 3D spatial freeze-frame of micro-seismic monitoring sources from hydraulic fracturing;iii.construct a hydraulic fracture density model using the intensity from the micro-seismic monitoring;and iv.implement a 3D visualization of the hydraulic fractures,relying on the spatial constraints of the density model,the hydraulic fracture indication model,and the properties of the hydraulic fractures.This proposed technical method was used to produce 3D visualizations of the hydraulic fractures in well X in the Jiao reservoir,China,and the 3D visualizations of the distribution,development,extent and cutting relationships of hydraulic fractures were successfully realized.The results show that this technical method can be used as a practical and reliable approach to characterize hydraulic fractures.