一种地震预警监测传感器模块的设计及实现

Design and Realization of a Seismic Monitoring Sensor Module

目前世界上地震预警系统基本都是通过地震台网来确定地震的震级并对地震进行定位,其预警准确性的提高主要依靠台网密度的增加。基于地震预警原理以及传感器技术,本文首次探讨了仅用单台地震监测传感器快速测定地震基本参数的可能性。设计了一种用于地震预警的地震监测传感器模块,阐述了确定地震参数的算法。该传感器模块能自动捡拾P波的到时,然后利用P波的初动信息确定地震的方位角,最后利用P波到达后前3s加速度数据确定地震的震级、震源距,并发出警告,达到地震监测及预警的目的。

Throughout the world, most of the existing seismic alarm systems calculate magnitude and locate an earthquake through the seismic network; the accuracy of early warnings is improved by increased network density. The accuracy of basic parameters of the earthquake will be corre- spondingly improved. However, it takes a lot of manpower, material, and other social and public resources to use this method. Meanwhile, the seismic network itself has shortcomings in the complexity of multi--stations and the vulnerability of the network system. Due to economic back- wardness and communication underdevelopment, most parts of our country still lack an earth- quake early warning system; these areas are in the earthquake belt, so it is necessary to provide a seismic alarm in this area. This paper is based on the principles of earthquake early warning, computer technology, and sensor technology. It introducess the principle of earthquake early warning and discusses the possibility of rapid determination of earthquake parameters using only a single seismic monitoring sensor module. We also complete the hardware and software design of the earthquake warning sensor module for seismic monitoring and expound the process to deter- mine earthquake parameters algorithm in detail. After an earthquake occurred, the P-wave of seismic propagated to the seismic monitoring station. First, the sensor module system was trig- gered using the short-term average/long-fterm average （STA/LTA） technique and the P-wave was picked up automatically. Second, on the basis of a traditional method, we used the initial motion direction of the three P wave components to determine the epicenter azimuth at the seismic monitoring station. Finally, we used the first motion displacement of the three P wave compo- nents to determine the epicenter azimuth. However, due to the high error of the azimuth based onthis method, we have improved it to calculate several seismic azimuths by using information from the P--wave initial motion, and the arithmetic mean is used as the final value of the azimuth. As earthquake magnitude has some mathematic statistical relation to the predominant period of the P- wave, and the maximum displacement amplitude of different earthquake magnitudes has a certain attenuation relation to the increase of the hypocentral distance, we calculated the predominant pe- riod and maximum displacement amplitude with the collected acceleration data during the first three seconds after the P-wave＇s arrival. Once the magnitude of the earthquake and the hypocen- tral distance are determined, a warning is sounded, achieving the goal of earthquake monitoring and early warning. The minimum acceleration the earthquake monitoring sensor module used here can distinguish is less than 1 gal, and the range of acceleration is ± 2 g. It also can collect acceler- ation of the three components simultaneously, and every sampling frequency could reach to 500 Hz. The power is 350 mW under normal conditions; it is thus suitable for outdoor use. The max- imum error range of the azimuth is ±15°,and the average error is 11°; compared to the 8.5° aver- age error of better seismic monitoring stations, the data here are a little larger, 2.5°, because the earthquake magnitude and hypocentral distance are calculated by two statistical relationships, and it has a ±0. 412 magnitude error and a±1.59 kilometers hypocentral distance error. Compared to the traditional way that seismic networks determine earthquake parameters, the basic parame- ter calculated here has a larger error, but it has a lower demand for a single earthquake monitor to determine basic parameter of the earthquake. So it is practicable to determine the basic parameter of an earthquake by a single earthquake monitor sensor module.