1996年5月3日内蒙古包头西M_S6.4级地震的震源机制研究

利用地幔波波形拟合和P波初动符号联合反演的方法，估计了1996年5月3日内蒙古包头西MS6．4级地震的震源机制．得到节面1（40°，70°，－174°），节面2（308°，84°，－20°）。主压力轴P（-13．95×1017Nm，262°，19°），主张力轴T（15．66×1017Nm，356°，10°），中性轴N（B）（1．52×1017Nm，112°，69°）．地震形成左旋走滑兼弱倾滑断裂，断裂面较陡．据ML≥3.0级的余震分布、Ⅷ度区的烈度分布以及宏观震中与微观震中的相对位置推测，节面2可能与实际的地震破裂面相近．据宽频垂直向（BHZ）波形记录中SP与P的到时差估计，震源深度约为21Km．

A STUDY FOR THE MECHANISM OF M_S 6.4 EARTHQUAKE ON MAY 3,1996,AT WEST BAO TOU,NEI MONGOL

The mechanism of Ms6.4 earthquake on May 3, 1996, at west Bac Ton, Nei Mongol, is estimated with a joint inversion method using mantle waveform fitting and P wave first inchon signs. Nodal plane l（40°, 70°,-174°）, nodal plane 2（308°, 84°,-20°）; principal compressive axis P（-13.95×1017Nm, 262°, 19°）, principal extensional axis T（15.66×1017Nm, 356°, 10°）, neutral axis N（B） （1.52×1017Nm, 112,69°） are obtained. The earthquake formed a left-lateral strike-slip and weak dipslip fault and the fault plane is steep. That nodal plane 2 may be near the actUal fault plane is inferred by the distribution of aftershocks with ML>3.0 and the distribution of earthquake intensity with degree m, as well as the relative position of macroscopic epicenter to the microcosmic one. That the source depth is about 21km was estimated by the bine differences betWeen sP and P arrival bine on BHZ channel.