UDC 550. 348.425.4
N. I. ShishkinThe seismic energy transferred to an elastic half-space as a result of a contact explosion and a meteorite impact on a planet's surface is estimated. The seismic efficiency of the explosion and impact are evaluated as the ratio of the energy of the generated seismic waves to the energy of explosion or the kinetic energy of the meteorite. In the case of contact explosions, this ratio is in the range of 10 −4 -10 −3 . In the case of wide-scale impact effects, where the crater in the planet's crust is produced in the gravitational regime, a formula is derived that relates the seismic efficiency of an impact to its determining parameters.Introduction. Estimating the seismic energy transferred to the medium as a result of underground explosions and impacts of space bodies on the Earth is important for predictions of the seismic effect on engineering facilities, biota, the Earth's crust, and the planet as a whole.The energy of seismic motion for underground atomic explosions is determined in [1], where it is shown that the seismic efficiency (SE) k s ≡ E s /E 0 (E s is the energy of seismic waves and E 0 is the energy of explosion) has the following values: 0.1% in alluvium, 1.2% in tuff, 4.9% in rock salt, and 3.7% in granite. These data were obtained for fairly great charge depths. As the charge depth decreases, the value k s increases. As shown in [2], a decrease in the charge depth results in an increase in the SE to a value close to 10%.The seismic efficiency of a high-velocity impact was evaluated in [3][4][5][6][7][8]. From the papers cited, it follows that the value of k s was estimated with a large error (k s = E s /E 0 = 10 −6 -10 −2 , where E 0 is the kinetic energy). Its dependence on the parameters determining the seismic effect of impacts is also unclear. The value k s for contact explosions is not known.The object of the present study is to obtain the functional dependence of the seismic efficiency on the determining parameters in the cases of contact explosions and high-velocity impacts.1. Confined Explosion. The seismic effect of a confined underground explosion in rock is described using the Haskell model [1]. The longitudinal P -wave generated by an explosion is characterized by the potential ϕ(t, r) of the displacement field u(t, r) of the form Here t is the time reckoned from the time of explosion, r is the distance from the point of explosion, c P is the propagation velocity of the longitudinal waves, and f (τ ) is a function of the source equivalent in the generated P -wave to the explosion. Relation (1.1) contains three free parameters: t 0 , Φ(∞), and B, which are chosen from experiments. The physical meaning of these parameters is as follows. The parameter t 0 determines the time scale