说明：  在压缩源激发下，真空-弹性表面的精确二维响应。（Garvin问题） 英文描述中有相关参考文献，对于做波场模拟的同学很有用。
(THIS FORTRAN PROGRAM CALCULATES THE EXACT SEISMIC 2D RESPONSE FROM A COMPRESSIONAL POINT SOURCE IN AN ELASTIC HALFSPACE WITH A FREE SURFACE. ALL GREEN S FUNCTIONS ARE CALCULATED ANALYTICALLY BY CAGNIARD-DE HOOP TECHNIQUE. CONVOLUTIONS WITH A GIVEN SOURCE TIME HISTORY ARE PERFORMED NUMERICALLY. References: de Hoop, A.T., 1960. A modification of Cagniard s method for solving seismic pulse problems, Appl. Sci. Res., B8, 349-356. Berg, P., If, F., Nielsen, P. and Skovgaard, O., 1994. Analytical reference solutions, in Modeling the earth for oil exploration, ed. Helbig, K., Pergamon Press, 421-427. Reference with example: Komatitsch, D. and Vilotte, J.P., 1998. The Spectral Element Method: En Efficient Tool to Simulate the Seismic Response of 2D and 3D Geological Structures, Bull. Seis. Soc. Am., Vol. 88, No.2, 368-392.)