2013年7月22日岷县、漳县Ms6.6地震发生后,我们立刻在极震区架设三台K2强震动记录仪器,以了解地震对黄土覆盖山地的影响,截至8月11日共获取地震记录172个(516条),M_L≥3.0的地震48个,最大震级M_L4.4,最大加速度值65.9 gal。我们从永星台阵的强余震观测资料中,选取震级较大的余震记录进行分析,经过初步处理,分别读取各个台站的地表最大加速度值,由于观测地区的黄土覆盖层较薄,土质松软,永星村台、永星小学台这两个台的加速度记录,不能与大竜村台的记录直接比较,我们将观测记录进行傅里叶分析,统计其优势频率,展示部分典型记录的傅里叶谱发现,黄土对高频成分的吸收作用不可忽视,最大加速度值随震中距的增大而衰减迅速。在近场情况下,地表最大加速度对震中距十分敏感,所以无法直接对比不同地形对于地表加速度的影响,分析结果表明:大竜村台优势频率为5.2 Hz;永星村台优势频率为4.1 Hz;永星小学台优势频率为5.3 Hz,注意到位于山脚下的大竜村测点为基岩,加速度记录的优势频率自然较高,而位于山顶的永星村是黄土地基,但是此地的加速度记录的优势频率明显高于山腰记录,几乎与基岩台基的优势频率相当。宏观调查也表明:低频率、高烈度对于房屋的破坏力更大M_L3.8地震观测表明,地表加速度值随震中距的增大而迅速衰减,距离最近的大竜村台(基岩台址)获取的加速度记录北南向最大,另外两个分向的加速度记录也大于较远的两个流动台的记录。基岩台北南向比垂直向要大,和这次地震的震源机制(逆冲兼走滑)相关。地形影响依然存在,本次观测台阵中,位于山顶的永星村观测记录的傅里叶谱,明显高于山腰的记录,地表最大加速度值也稍高于山腰观测,由于地形相差不够大,规律性也不太明显,本次观测结果和以往在孤立山峰的观测情况略有不同,一是记录地震的震级偏小,而观测距离又偏近,震中距的影响可能超过地形因素的影响程度,所以其原因更加复杂,有待进一步研究。 July 22, 2013 After the Ms6.6 Minxian County and Zhang County Ms6.6 earthquakes occurred, we immediately set up three K2 Strong Vibration recording instruments in the extremely shock zone to understand the impact of earthquakes on loess-covered mountains. As of August 11, a total of 172 earthquakes (516), 48 earthquakes with M_L≥3.0, maximum magnitude M_L4.4 and maximum acceleration of 65.9 gal. From the strong aftershock observation data of the Wuxing Array, we select the aftershock records with large magnitudes for analysis. After preliminary processing, we read the maximum surface acceleration of each station. Because the loess layers in the observation area are thin, Soft, Yongxing Village, Yongxing primary station acceleration records of these two stations can not be directly compared with the record of Taihaku Village, we Fourier analysis of the observation records, statistics of the dominant frequency, showing some of the typical records of the Fu Lime spectrum found that the absorption of high frequency components of loess can not be ignored, the maximum acceleration value decreases rapidly with the epicenter distance increases. In the near-field case, the maximum surface acceleration is very sensitive to the epicenter distance. Therefore, it is impossible to directly compare the effects of different terrains on the acceleration of the ground. The analysis results show that the dominant frequency of the Daban Village is 5.2 Hz, that of the Yongxing Village is 4.1 Hz, The dominant frequency of Yongxing Primary School Station is 5.3 Hz. It is noted that the measuring point at Dayao Village located at the foot of the mountain is bedrock, and the natural frequency of acceleration recording is naturally high. However, the Yongxing Village at the top of the mountain is loess ground. However, The dominant frequency was significantly higher than the mountainside record, almost equal to the dominant frequency of bedrock base. The macro survey also shows that low frequency and high intensity have more destructive effects on the houses. The M_L3.8 earthquake observation shows that the acceleration of the earth surface rapidly decays with the increase of the epicentral distance. The nearest Dazhu village (bedrock site) The acceleration record is north-south to the maximum, and the acceleration records for the other two orientations are also greater than those recorded for the two far mobile stations. The south of basement in Taipei is larger than the vertical and related to the focal mechanism (thrust and slip) of the earthquake. The terrain impact still exists. In this observatory array, the Fourier spectrum of observation records at Yongding Village located on the top of the mountain is obviously higher than the records of the mountainside. The maximum acceleration of the surface is also slightly higher than that of the mountainside observation. Because the difference of the terrain is not big enough, The regularity is not obvious. This observation result is slightly different from the previous observation of isolated peaks. The first is that the magnitude of the earthquake is recorded to be small and the observation distance is too close. The epicentral distance may be affected by the impact of topographical factors , So the reason is more complicated, pending further study.