利用P波参数阈值实时估算地震预警潜在破坏区范围

Real-time estimation of potentially damaged zone for earthquake early warning based on thresholds of P-wave parameters

  • 摘要: 由于传统的潜在破坏区范围估算方法只能在已获取到震中位置和地震事件结束后才能产出,且往往需要数分钟的耗时,其实时性已无法满足地震预警要求。因此,为了快速产出潜在破坏区范围估算结果并将其用于预警,本文采用了一种结合现地预警技术和区域预警技术、基于预警参数(位移幅值Pd和特征周期τc)阈值的实时潜在破坏区范围估算方法。首先利用国内地震事件(4.0≤MS≤8.0)的记录数据和日本强震动观测事件(6.5≤MJ≤8.0)的数据拟合出特定的适应于我国的参数关系式,包括τc与震级M的相关性、Pd与峰值速度PGV的相关性以及Pdτc和震源距R的相关性;其次,根据最小震级(MS6.0)和仪器烈度(Ⅶ度)定义相应的参数阈值(Pd=0.1 cm和τc=1.1 s);最后,利用已有的3次破坏性地震事件数据开展线下模拟,对该方法的适应性和时效性进行了验证。结果表明,对于2013年MS7.0四川芦山和2014年MS6.5云南鲁甸两次中强地震,震后约10 s即可获取到比较稳定的潜在破坏区范围估计结果;而对于2008年MS8.0汶川特大地震,在其记录台站分布密度不高的情况下,震后40 s左右的估算结果始呈稳定状态。

     

    Abstract: Conventional methods used for potentially damaged zone (PDZ) estimation usually take several minutes to produce the results, which are generated only after the epicenter of an earthquake has been acquired and the seismic event has ended, its real-time performance cannot meet the requirements of earthquake early warning (EEW). Therefore, to rapidly produce the estimated range of PDZ for EEW, in this paper, we adopted a real-time method to estimate the PDZ range. The method is an integrated on-site and regional early-warning method based on the predefined thresholds of two early-warning parameters, the peak displacement (Pd) and characteristic period (τc). Firstly, we used seismic events records with MS between 4.0 and 8.0 from the China Strong Motion Networks Center and strong-motion records with MJ between 6.5 and 8.0 downloaded from the Japanese National Research Institute for Earth Science and Disaster Resilience to linearly fit relationships of early-warning parameters, including τc versus M, Pd versus PGV, and Pd as a function of τc and hypocentral distance R. We then defined two early-warning parameters thresholds which are set for a minimum magnitude MS6.0 and instrumental intensity Ⅶ, according to the empirical regression analyses of the applied data. At each recording site, the alert level is assigned based on a decisional table with four alert levels defined upon critical values of the parameters Pd and τc. These two threshold values are Pd=0.1 cm and τc=1.1 s. Given a real-time, evolutionary estimation of earthquake location from first P arrivals, the method furnishes an estimation of the extent of PDZ as inferred from continuously updated averages of the period parameter and from mapping of the alert levels determined at the near-source seismic stations. Finally, to test the method’s efficiency and rapidity on mapping the damage zone in a few seconds after an earthquake occurrence, we offline applied the methodology to the strong-motion records of three destructive seismic events. The results show that a robust estimation of the PDZ range for moderate-to-large earthquakes like the 2013 MS7.0 Lushan and 2014 MS6.6 Ludian events can be obtained at about 10 s after the earthquake occurrence. And for the Wenchuan giant earthquake, as the case of low density of recording stations, the prediction of the PDZ becomes stable about 40 s after its occurred time.

     

/

返回文章
返回