Love waves excited by discontinuous propagation of a rupture front

Summary. Analytical results are presented for Love waves generated by sudden changes of the rate of advance of a curved rupture front in an inclined fault plane that is embedded in an elastic half‐space. The boundary condition at the surface of the half‐space approximates the presence of an overlying layer. The calculation consists of two parts. First, ray theory is used to calculate far‐field approximations to the horizontally polarized wavefields which are emitted when the speed of the rupture front suddenly changes. These fields can be expressed as products of emission coefficients (which govern the angular dependence) and propagation terms. Secondly, a representation integral for the Love wave over a surface enclosing the rupture front is constructed, using the emitted signal and an appropriate Green's function. This integral is evaluated asymptotically. The resulting approximate Love‐wave spectrum shows an explicit dependence on the nature of the rupture process, on the rupture‐front and fault‐plane geometry, and on the magnitude of a sudden change in the rate of advance of the rupture front.