江苏高邮—宝应MS4.9地震强震动观测与记录分析

Strong Motion Observation and Records of the Gaoyou BaoyingMS4.9 Earthquake in Jiangsu Province

摘要:

2012年7月20日江苏高邮—宝应交界处发生MS4.9地震，对江苏省数字强震动台网43个台站获取的强震记录进行初步分析得出，地震的最大水平向加速度为33.76 cm/s2，并计算地震的仪器烈度，得出烈度分布等值线图，与地震现场实际调查的烈度分布情况基本一致。

Abstract:

The strong motion of the Gaoyou-Baoying MS4.9 earthquake occurring on July 20，2012，was recorded by 43 of 50 strong motion stations in Jiangsu Province.The observation system of every strong earthquake station includes the Etna strong motion recorder produced by the KMI Company in addition to a domestic force balance accelerometer（FBA） sensor.These instruments effectively recorded the earthquake ground motion that occurred in Jiangsu Province by setting the appropriate threshold and transmitting the strong motion events through PSTN or CDMA wireless networks to the digital strong motion network center of Jiangsu Province.During this earthquake，the recorded maximum acceleration was 33.76 cm/s2.The earthquake epicenter was located at 33.04°N，119.57°E，and the focal depth was approximately 6 km.The microcosmic-epicenter was located in Shuanggou Village，Gaoyou City，where strong earthquake motion was felt.Tremors were felt throughout Jiangsu Province，as well parts of Anhui Province at its junction with Jiangsu Province. Fourier spectral analysis was used to determine that the seismic acceleration included abundant frequency components mainly between 2 Hz and 4 Hz. The acceleration time history and Fourier spectrum records from several strong ground motion stations are also given in this paper.Moreover, this study gives a brief introduction of the American ShakeMap system，which is the primary method used to calculate instrument intensity，and a recommended intensity scale provided.We collected recent strong earthquake records of Jiangsu Province and fit the instrumental intensity calculation formula （below intensity of VI）with these strong earthquake records.Due to the limited earthquake records in this region, however，we were unable to give a complete intensity calculation formula.Finally，two methods of producing an intensity contour map are given in addition to comparisons between approaches and conclusions.The characteristics of the seismic intensity contour are intuitive and vivid，which makes it easier to more accurately describe the distribution characteristics of earthquake damage.The results from the analysis of spectral characteristics with the strong motion records show that the peak acceleration of the horizontal component is larger than the vertical component.Moreover，the site covering of soil has an obvious amplification effect.On the basis of the strong motion records and influence of the field contour map，we obtained the peak acceleration distribution of the Jiangsu area.These result conform those of the actual investigation.The result of using the strong motion data to quickly assess the spatial distribution of seismic intensity has important significance for the earthquake emergency rescue work.Therefore，the method used in this study has a certain degree of feasibility. It is difficult to calculate instrument intensity values that are consistent with macroscopic intensity values because of objective factors such as subjectivity，and vagueness that exist in the evaluation of seismic intensity.Therefore，by selecting a suitable method for intensity evaluation of ground motion parameters and examining the seismic ground motion attenuation relationship，in addition to researching methods of field calibration for future work，the instrument intensity calculation method is proven to be scientific and reasonable.