Abstract:By using the seismic source model of crack containing hyperpressure gas[1],the distribution of the first motion mark of P wave is studied.According to the deduction,the cracks containing hyperpressure gas with different inclination can form the distribution pattern in four quadrants of first motion mark of P wave and the nodal lines of P wave in the shape of conic section,such as circle,ellipse,parabola and double-curve etc..According to the shape of nodal lines of P wave and type of instability,the earthquakes are classified.The distribution feature of first motion amplitude of P and S waves and the feature of ground deformation etc.deduced correspond with practice.
