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作者从断裂力学观点研究了圆盘形纯剪切破裂产生的远场位移,导出了远场位移的解析表达式.用此表达式计算了远场位移脉冲波形及其谱.求得了P波和S波拐角频率F_(cα)、f_(cβ)与震源破裂半径的关系式,t_(2α)和t_(2β)分别是P波与S波的震源脉冲宽度在震源球上的平均值.V_r是破裂速度,取0.775β,α、β是P波与S波速度.介质吸收的影响,假定在略去路径滞后因子e-(iωr)/c后是最小相移滤波器,应用希尔伯特(Hilbert)变换导出了介质的频率响应公式式中,r为震源距,c为波速,Q为介质品质因数,ω_m为高频截止频率.它与富特曼(Futterman)公式是不一样的.在考虑了介质吸收影响与仪器频率特性影响后,在频率域中求出了震源尺度2a和地震矩M_0.在时间域中,利用快速傅立叶反变换求出介质和仪器的脉冲响应后与震源脉冲折积,求得了合成地震图,用此图得到了地震图初动半周期T_(2P)与震源尺度2a或震源脉冲宽度t_(2a)之间的关系量板.用此量板在时间域中也求得震源尺度2a,与频率域中求得的结果基本一致. 利用从断裂力学观点研究震源破裂过程导出的关系式求出了京津唐张地区的区域剪切应力τ_0,式中η为地震辐射效率,取0.05;v为泊松比,取0.252;μ为刚性模量,取3.3×10~(11)达因/厘米~2.结果表明,1976年7月28日唐山大震前,唐山—丰?
The far field displacement caused by the disc-shaped pure shear failure is studied from the fracture mechanics point of view, and the analytical expression of far-field displacement is deduced.The far-field displacement pulse waveform and its spectrum are calculated by this expression.The P-wave and The relationship between the frequency of corner wave F_ (cα), f_ (cβ) and the rupture radius of the source wave, t_ (2α) and t_ (2β) are the mean values of the source pulse widths of P- and S- Is the rupture speed, taking 0.775β, α and β are the P-wave and S-wave velocities. The influence of medium absorption, assuming that the path-delay factor e- (iωr) / c is neglected, is the minimum phase- Hilbert transform derives the frequency response formula of the medium, where r is the source distance, c is the wave velocity, Q is the medium quality factor and ω_m is the high-frequency cut-off frequency, which is different from the Futterman formula After taking into account the influence of medium absorption and the frequency characteristics of the instrument, the source scale 2a and the seismic moment M_0 were found in the frequency domain.In the time domain, the impulse response of the medium and the instrument was obtained by inverse fast Fourier transform The result of the synthetic seismogram is obtained by using the pulse truncation and the seismogram. The first half period T 2 P and seismogram of the seismogram are obtained, Scale 2a or source pulse width t 2a The volumetric plate is also obtained from the time domain using this plate in the time domain, which is basically the same as the one obtained from the frequency domain.Using the theory of fracture mechanics, Rupture process derived derived relationship between Beijing and Tianjin Tangzhang area of regional shear stress τ_0, where η is the seismic radiation efficiency, take 0.05; v Poisson’s ratio, take 0.252; μ is the modulus of rigidity, take 3.3 × 10 ~ (11) dyne / cm ~ 2. The results show that before July 28, 1976 Tangshan earthquake, Tangshan - Feng?