Evaluation of early warning capability of Fujian Province seismic network
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摘要: 由于常用的均方根值法和噪声功率谱法不能消除不同传感器记录的噪声干扰,为提高噪声水平计算的准确度,本文选用最大概率峰值位移作为背景噪声评估指标。基于可靠的噪声数据,借鉴震级-最大距离监测能力法并考虑预警时效,提出了地震预警最小震级评估方法,系统评估福建三类传感器网及其融合网的地震预警最小震级和预警首报时间。结果表明:测震强震融合网的地震预警最小震级高于单测震网,但明显低于强震网;强震烈度计融合网与单烈度计网的结果相近;三网融合后95%区域的地震预警最小震级约为ML3.2。由于烈度计网比测震和强震网密集,其预警首报时间最短;三网融合相对于单测震网或单强震网,其震后地震预警首报时间得到了明显缩短,预计95%区域的首报时间为4—6 s。本文研究为福建省的台网布局的优化和重点区域监测能力的提升提供了参考依据。Abstract: Since the common root-mean-square method and noise power spectrum method cannot eliminate the noise interference recorded by different types of sensors, we use the maximum probability peak displacement as the background noise evaluation index to calculate the noise level more accurate. Based on the reliable noise data, referring to the magnitude maximum distance monitoring capability method and considering the timeliness of earthquake early warning (EEW), an EEW minimum magnitude evaluation method is proposed. This new method can systematically evaluate the minimum magnitude of EEW and the warning time of independent three types of sensor networks and their fusion networks in Fujian. The results show that the minimum magnitude of EEW based on the fusion networks of the seismometer and the strong seismometer is higher than that of the single seismometer network, and obviously lower than that of the strong seismometer network. For fusion networks of strong seismometer and intensity meter, the minimum magnitude of EEW is similar to that of single intensity meter network. After integrating three types of networks, the minimum magnitude of EEW in 95% regions is about ML3.2. Because the density of intensity meter network is higher than the seismometer and strong seismometer network, the warning time is the shortest. Compared with the single seismometer network or single strong seismometer network, the warning time of EEW has been significantly reduced by three types sensor fusion networks, and the warning time in 95% regions is 4−6 seconds after an earthquake occurred as it is estimated. This study provides a reference to optimize the distribution of networks and increase the monitoring capacity of key regions in Fujian province.
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Keywords:
- noise level /
- intensity meter /
- earthquake early warning /
- monitoring capacity /
- timeliness
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图 3 地震计、强震仪与烈度计的背景噪声PGD值统计散点图(a)、直方图(b)和累计概率分布图(c)
图(a)中红色虚线为正常PGD值的上下限
Figure 3. The scatter plots (a),histograms (b) and cumulative probability distributions (c) of background noise PGD of seismometer,strong seismometer and intensity meter
The red dotted line in Fig.a is the upper and lower limit of normal PGD value
图 8 各种仪器单网及不同组合网的地震预警首报时间空间分布
(a) 地震计;(b) 强震仪;(c) 烈度计;(d) 测震强震融合;(e) 强震烈度计融合;(f) 测震强震烈度计
Figure 8. Space distribution of warning time for single network and fusion networks of various fusion networks
(a) Seismometer;(b) Strong seismometer;(c) Intensity meter ;(d) Seismometer and strong seismometer fusion ;(e) Strong seismometer and intensity meter fusion ;(f) Seismometer,strong seismometer and intensity meter fusion
图 9 各种仪器单网及不同组合网的地震预警首报时间直方图(上)和累计概率分布图(下)
(a) 地震计;(b) 强震仪;(c) 烈度计;(d) 测震强震融合;(e) 强震烈度计融合;(f) 测震强震烈度计
Figure 9. Histogram (up) and cumulative probability distribution diagram (down) of warning time for single network and different fusion networks of various instruments
(a) Seismometer;(b) Strong seismometer;(c) Intensity meter ;(d) Seismometer and strong seismometer fusion ;(e) Strong seismometer and intensity meter fusion ;(f) Seismometer,strong seismometer and intensity meter fusion
图 10 各仪器单网和不同组合网的地震预警最小震级空间分布
(a) 地震计;(b) 强震仪;(c) 烈度计;(d) 测震强震融合;(e) 强震烈度计融合;(f) 测震强震烈度计融合
Figure 10. Spatial distribution of EEW minimum magnitude of single network and fusion networks of various instruments
(a) Seismometer;(b) Strong seismometer;(c) Intensity meter ;(d) Seismometer and strong seismometer fusion ;(e) Strong seismometer and intensity meter fusion ;(f) Seismometer,strong seismometer and intensity meter fusion
图 11 各仪器单网和不同组合网的地震预警最小震级直方图(上)和累计概率分布图(下)
(a) 地震计;(b) 强震仪;(c) 烈度计;(d) 测震强震融合;(e) 强震烈度计融合;(f) 测震强震烈度计融合
Figure 11. Histogram (up) and cumulative probability distribution (down) of EEW minimum magnitude of single network and fusion networks of various instruments
(a) Seismometer;(b) Strong seismometer;(c) Intensity meter ;(d) Seismometer and strong seismometer fusion ;(e) Strong seismometer and intensity meter fusion ;(f) Seismometer,strong seismometer and intensity meter fusion
表 1 三类传感器传统的监测震级值
Table 1 The traditional monitoring magnitude of the three types of sensors
台网类型 最小ML 平均ML 最大ML 累计概率55%时的ML 累计概率95%时的ML 测震台网 0.9 1.9 2.5 1.9 2.4 强震台网 1.7 2.7 3.4 2.7 3.2 烈度计台 2.7 3.0 4.4 3.0 3.5 表 2 单网和多网融合的地震预警首报时间
Table 2 The warning time of EEW for single network and fusion networks
台网类型 最小值/s 平均值/s 最大值/s 累计概率55%/s 累计概率95%/s 测震 1.0 5.0 12.9 4.9 9.1 强震 1.0 5.2 18.1 4.9 10.7 烈度计 1.0 1.6 4.8 1.5 2.8 测震强震融合 1.0 3.3 12.9 3.2 6.9 强震烈度计融合 1.0 1.5 4.8 1.4 2.7 三网融合 1.0 1.5 12.9 1.3 2.8 表 3 单网和多网融合的地震预警监测震级
Table 3 The monitoring magnitude of EEW for single network and fusion networks
最小ML 平均ML 最大ML 累计概率为55%时的ML 累计概率95%时的ML 测震 0.9 2.0 2.8 2.0 2.5 强震 1.7 2.9 4.2 3.0 3.8 烈度计 2.7 3.0 4.5 3.0 3.6 测震强震融合 0.9 2.2 3.9 2.2 3.0 强震烈度计融合 1.7 3.0 4.5 2.9 3.5 三网融合 0.9 2.8 4.3 2.9 3.2 -
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