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International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) pp. 1-10 http://dx.doi.org/10.21742/ijitbd.2016.1.1.01 Research on Intensity Quick Report and the Key Technology of Seismic Intensity Monitoring Laibao Yu1, 2 and Tao Zhang1, 2 Institute of Geophysics and Geomatics, China University of Geosciences Wuhan 430074 2 Wuhan City Vocational College, Wuhan 430064 Wuhan, China, 430074 [email protected] 1 Abstract Combined with the status quo of intensity monitoring and intensity quick report system at home and abroad, the present paper studies the key technologies of the intensity quick report system, including the technical parameters required of seismic monitoring device and hardware implementations, quick report system components and networking, intensity calculation model, software of the system etc., and conducts a preliminary test. After testing, the seismic monitoring device designed has good sensitivity and amplitude-frequency characteristics. The system can send data, receive data and calculate intensity quickly, meeting the requirements of intensity quick report. Keywords: intensity quick report, seismic, network, design scheme 1. Introduction Although China has a lot of earthquakes, China is one of the most vulnerable nations of earthquake in the world, so far a real seismic intensity quick report system has not been established in the mainland of China. Combined with the status quo at home and abroad, the present paper studied the key technology of seismic intensity quick report system. Seismic intensity quick report system get real-time data from seismic monitoring network in advance layout. When the acceleration of monitoring nodes exceed the setting threshold value, the data will be sent to the server through the network. The server analyzes the data and calculates the intensity and judges the number of the node exceeding the setting threshold value, so as to determine whether issue an emergency disposal instruction. Seismic intensity quick report system contains seismic information acquisition, information transmission, intensity calculation and other key parts. 2. The acquisition of seismic information 2.1. Device for obtaining seismic information At present, there is no clear standard about instrument index of earthquake early warning system in China, through the analysis of the technical parameters of instrument used in existing earthquake early warning system, the present study summarizes the key indexes of seismic pick-up device in earthquake early warning system [1]. IJITBD Copyright ⓒ 2016 GV School Publication International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) Table 1. The table of the basic parameters of the seismic monitoring device Countries and Regions Type Range Frequency Range Dynamic Range Transverse sensitivity American Japan Taiwan Turkey 3-axis 3-axis 3-axis 3-axis ±4g ±4g ±2g ±2g DC~200HZ DC~100HZ DC~50HZ DC~50HZ 155dB 96dB 108dB <0.03g/g <0.03g/g 3dB From the table, we can see the vibration pick-up device of early warning system generally meet 3-axial measurement range , range≥2g, frequency response DC~50HZ, dynamic range ≥100db. In recent years, the rapid development of MEMS offers an opportunity to the development of earthquake prevention and disaster reduction constrained by seismic instruments cost. By comprehensive comparison, HAAM-326B1 is selected as the acceleration measurement chip. The basic parameters of HAAM-326B1 are as follows: the range of ± 2G, the frequency range of DC~250HZ, the transverse sensitivity <5%, withstand the maximum impact of 5000g. Its performance meets the requirements. GND HAAM326B CPU STANDBY +3V Vcc +3V xout VCH0 LTC1865 yout VCH1 zout VCH2 LTC1865 C8051F P2.0 020 P2.1 CONV_1 P2.2 SDO_2 P2.3 SCK_2 P2.4 CONV_2 P2.5 SDO_1 SCK_1 Figure 1. The hardware structure chart As shown in fig.1, 16 bit double channel A\D chip LTC1865 is selected as data acquisition chip. HAAM-326B1 integrates signal low pass filter circuit inside, the user only need to provide the external capacitor to realize low-pass filter. Filter capacitance can be calculated by the following equation. F−3dB = 1 (2π × Rout (32k Ω) × Cx, y, z ) (1) Considering the frequency range of natural earthquake, the setting of the cut-off 2 Copyright ⓒ 2016 GV School Publication International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) frequency is 50HZ. Low pass filter capacitor is 0.1uf through calculation. In order to improve the precision of A\D, the device with an external precision voltage reference source MAX873 is used. 2.2. Anti-interference Design Seismic signal is weak and vulnerable to be interfered, so it is important to take measures to reduce the interference. There are many factors causing interference, including the signal channel interference and power supply interference etc. [2]. Anti-interference methods are mainly the following: 2.2.1 Ground connection Grounding is the main method for interference suppression. Proper grounding can eliminate the noise voltage generated when the circuit current flows through the common ground resistance. The signal frequency of the system is below 1 kHz, belonging to the low frequency circuit. The inductance between the wiring and components is not the main problem, but when the grounding forms a loop, it will cause a great deal of interference on the circuit, so take one point grounding. Further, the power supply line and the signal line should be separated in the PCB wiring .In addition, in order to remove the coupled simulation of the integrated circuit and reduce the noise, when design the analog circuit connect the spare pins of analog chip to high level or GND through resistor. 2.2.2 Filtering Filtering is divided into power supply filtering and signal filtering. A simple power supply filter circuit and the EMI flake filter with magnetic beads are adopted .After filtering, the noise of the circuit is significantly reduced; Signal filtering is mainly to reduce the use of capacitive and inductive energy storage element to decrease the mean square values of thermal noise. 3. Network and signal transmission The seismic intensity quick report system, including an information processing server, special transmission network, monitoring node, network interconnection equipment, and emergency disposal device etc., is a complex system. The architecture frame of urban intensity quick report system is shown in the Fig.2. When the earthquake occurs, the seismic data monitored by the monitoring node is sent to the server through a dedicated network; The server quickly analyzes the data, estimates the seismic parameters, evaluates the effects of range, and finally makes the integrated decision by integrating the engineering condition, seismic vulnerability and other information. 3.1. Monitoring node The main function of the monitoring node includes collection of strong motion data, trigger judgment, storage and upload of the vibration data before and after the trigger, fault self-checking, and periodically sending node running status etc. 3.2. Transmission Network Copyright ⓒ 2016 GV School Publication 3 International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) Transmission network consists of the backbone nodes which are arranged in the place having better installation environment with higher reliability than other monitoring nodes. Transmission network transmits the strong motion data got from backbone nodes and other nodes to data processing server, and transmits the instructions of data center to each backbone node. Lay special network as the backbone network and use the IPv4 protocol as internet address allocation Special network is connected into the public network through the firewall. Figure 2. The architecture frame of network and signal transmission 3.3. The server and client The server is the central module of the whole city intensity reporting system. It’s a set of software system installed on the computer system, and it can realize remote control, data processing, human-computer interaction and so on, so as to analyze and publish the data obtained, so as to achieve the ultimate goal of intensity quick report system design. 4. Intensity calculation The current Chinese seismic intensity scale gives the reference relationship between two physical parameters which are the horizontal peak ground motion acceleration and peak velocity and seismic intensity above V degree. When calculate the intensity using PGA and PGV respectively, the coincidence rate of the result of calculation and field survey intensity is very low. The intensity calculation methods of Japan Meteorological Agency use almost all 4 Copyright ⓒ 2016 GV School Publication International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) parameters of ground motions, and have high coincidence rate. After comprehensive consideration, the system adopts the main idea of the Japanese intensity calculation, combined with Chinese geological and structural characteristics, properly modified the parameters of the algorithms 'duration', and finally it achieves good results. The specific steps of the algorithm are described in detail as follows [3]. Earthquake acceleration time history of three directions gi (t ) gets by Fourier transform respectively. The results Gi (ω ) , multiplied by three kinds of filter function,gets the function G 'i (ω ) G 'i (ω ) = Gi (ω ).F1 (ω ).F2 (ω ).F3 (ω ) (2) Formula parameters are defined as follows: F1 (ω ) = (1/ ω )1/2 F2 (ω ) = 1 (1 + 0.694 x + 0.24 x + 0.0557 x 6 + 0.009664 x8 2 4 +0.00134 x10 + 0.000155 x12 ) F3 (ω ) = (1 − exp(−ω / ω0 )3 ) = = x ω= Hz , ω0 0.5 Hz / ωc , ωc 10 ω is the frequency of seismic wave ' ' Third, the gi (t ) is obtained by the inverse Fourier transform of G i (ω ) . Fourth, the three time history components are synthesized into vector acceleration A= g1' (t ) 2 + g 2 ' (t ) 2 + g3' (t ) 2 Fifth, guarantee (3) τ ( Am ) ≥ 0.3s = I JMA 2.log Am + 0.94 , then get the Sixth, put equivalent acceleration A into the formula intensity. Copyright ⓒ 2016 GV School Publication 5 International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) START i=1,3 FFT Gi (ω ) ← gi (t ) G 'i (ω ) = Gi (ω ).F1 (ω ).F2 (ω ).F3 (ω ) FFT −1 gi ' (t ) ← G 'i (ω ) Vector acceleration v (t )(t = 1, n) k =1 Select data set v(k ), v(k + 1),...v(k + j ) k= k + l Sort s (1), s (2),...s ( j + 1) Dert min e vector amplitude a0 (k ) = s (m) Calculate IISI IISI (k ) END Figure 3. The flow chart of intensity calculation 5. Software Design 5.1. Processing of the monitoring node [4] (1) If the personal device used as a seismograph detects the acceleration exceeding a fixed threshold value, a client program installed in the personal device will be in a transmission standby state. (2) When a measurement value exceeds a threshold value, the client program transmits the data of the instantaneous acceleration, time, and latitude longitude to a regional server. (3) After sending data to the server, the client records acquired acceleration and acceleration for N seconds, and the recorded data is transmitted to the server. This operation is repeated a few times at intervals of N seconds. (4) When the server processes data from many clients and decides the detected oscillation as a big earthquake, the earthquake information is sent to many clients in the area. 6 Copyright ⓒ 2016 GV School Publication International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) Start Start Initialization of the system Wait state Acceleration exceeding the threshold value Receive data N N Y Y Transmitted the value to server Data recording 2 seconds Calculation of intensity values Intensity exceeding the threshold value N Transmitted the data array to server Y The number of measuring points beyond the intensity>N N Y Start the emergency device Figure 4. Software Flow Chart 5.2. Processing of the server Each detailed operation is represented as follows: (5) A regional server maintains a standby state until much of data is received. On this state, the server program preserve data sent from clients to DB. (6) When the number of data reception reaches gets over a threshold, the server program starts a decision process of seismic intensity using received data in DB. (7) When the server program judged that a big earthquake happened, an alarm is sent to many clients. (8) After the first alarm was dispatched, the server program continues to receive data at the fixed interval from many clients, and sends alarms which raised accuracy gradually. 6. System verification 6.1. Monitoring node test Copyright ⓒ 2016 GV School Publication 7 International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) Fixed the monitoring node and standard accelerometer on the vibration table at the same time. Changed the frequency of the vibration table, recorded the acceleration of monitoring nodes and standard accelerometer, then obtained the normalized amplitude-frequency characteristics monitoring node [5] [6][7]. Test results are shown in Table 2. As seen from the results, the data collected by calibrated intensity meter is accurate, and it can be used as the basis data for calculating the intensity. Table 2. Test results of amplitude-frequency characteristics Frequency (Hz) X-axis/Standard sensor Y-axis/Standard sensor Z-axis/Standard sensor 1.0 1.001 1.000 1.001 3.0 0.999 1.001 1.001 10.0 1.000 1.001 1.000 30.0 1.001 1.000 1.000 6.2. Data transmission test Set the trigger threshold as 0.01g on the server, fix one monitoring node on the vibration table and make the vibration table simulate seismic waves, and observe whether the server receives and records vibration waveform. Figure 5. Simulated earthquake wave After testing, the system can be triggered, and it can record data. 6.3. Intensity quick report test The vibration table is used for quick report test. Fix three monitoring nodes on the vibration table at the same time, and make the vibration table simulate seismic waves, and observe whether the system generates an alarm or not. After test, the software responds quickly, and it can quickly give intensity values [8]. 7. Summary The research on the key technology of intensity quick report, including ground vibration monitoring, data transmission, and intensity calculation and so on was carried out. The present study completed the design work, including the design of ground motion detection device, data transmission and the design of intensity calculation model, and finally conducted the relevant analysis and experiment. 8 Copyright ⓒ 2016 GV School Publication International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) References [1] F. Jihua, W. Jianjun, L. Zhitao, L. Xiaoxi, W. Ronghui. “A new seismic emergency auto-handling instrument for the lifeline engineering: low cost embedded system solution”, 2010 International Conference on Intelligent Computation Technology and Automation.p242-245 [2] T. Uga, “An Emergency Earthquake Warning System Using Mobile Terminals with a Built-in Accelerometer”, 2012 12th International Conference on ITS Telecommunications.p837-842. [3] Y. Li, H. Fang, “Modeling and Analysis of Networked Control Systems with Network-Induced Delay and Multiple-Packet Transmission”, ICARCV 2008, p 494-498, 2008. [4] S. Hu, “Principles of Automatic Control”, Fourth edition. Beijing: National Defense Industry Press.2001.2:20~21 [5] F. Yamazaki, Y. Shimizu, W. Nakayama, “New development of super-dense seismic monitoring and damage assessment system for city gas networks,” Structural Safety and Reliability, p. 1-8, 2001. [6] Shake Table II of , http://www.quanser.com/english/html/earthquake/fs_overview.htm [7] P2P earthquake Information, http://www11.plala.or.jp/taknet/p2pquake/ [8] Z. Wu, “Concurrent Product Design and Seismic Analysis for Fuel Handling Equipment”, 2010 IEEE.p200-204. Author Yu-Laibao, (1984- ), mainly engaged in instrumental research. Copyright ⓒ 2016 GV School Publication 9 International Journal of Internet of Things and Big Data Vol. 1, No. 1 (2016) 10 Publication Copyright ⓒ 2016 GV School