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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．
Using the method of mantle wave fitting and P wave initial mapping joint inversion, the focal mechanism of Baotou West MS6.4 earthquake on May 3, 1996 is estimated. Section 1 (40 °, 70 °, -174 °) and section 2 (308 °, 84 °, -20 °) were obtained. The main pressure axis P (-13.95 × 1017Nm, 262 °, 19 °), the main tension axis T (15.66 × 1017Nm, 356 °, 10 °) and the neutral axis N (B) (1.52 × 1017Nm , 112 °, 69 °). The earthquakes form left-lateral strike-slip and weak-dip slip faults with steeper fracture surfaces. According to the distribution of aftershocks of ML≥3.0, the intensity distribution of Ⅷ degree area and the relative positions of macro-epicenter and microseism epicentral area, nodal 2 may be similar to the actual seismic rupture. According to the estimation of the arrival time difference between SP and P in the waveform of vertical and horizontal broadband (BHZ) waveform, the focal depth is about 21Km.