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Key Words explosive eruption, magma water vapor explosion, mass extinction, shock wave therapy, gene delivery
Abstract Shock wave research was traditionally developed as an element of high-speed gas dynamics supporting supersonic flights and atmospheric reentry of space vehicles. However, recently its scope has expanded to the comprehensive interpretation of shock wave phenomena in nature and the artificial world. In particular, many aspects of volcanoes's explosive eruptions are closely related to shock wave dynamics. One hypothesis proposes that during asteroid impact events that took place millions of years ago underwater shock waves played a decisive role in mass extinction of marine creatures. Shock waves have been successfully applied to medical therapy. Extracorporeal shock wave lithotripsy (ESWL) was a wonderful success in noninvasive removal of urinary tract stones. Recently, shock wave therapy was further developed for the revascularization of cerebral embolism, drug delivery, and other interesting therapeutic methods. This review provides an overview of the state-of-the-art interdisciplinary applications of shock wave research to geophysics and medicine.
1. INTRODUCTION
Shock wave is a comprehensive representation of a nonlinear wave motion occurring in a system in which a particle velocity and a propagation speed of information or sound speed coexist. Shock waves are created when the former has a value comparable to or exceeding that of the latter. Glass (1975) mentioned that shock waves exist in nature and the artificial world and emphasized that a shock tube is the test tube of modern gas dynamics for examining shock wave phenomena. He also reviewed current shock wave research directed to hypersonic flow research and briefly mentioned its merit to human welfare (Glass 1987).
Recently, shock wave research has expanded to other fields of science and technology. In 1990, the Japan Society of Shock Wave Research was restructured and began to promote interdisciplinary applications of shock wave research to medicine, geophysics, and industries (Takayama 1995). Based on these domestic activities, this review describes applications of shock wave research to geophysics and medicine.
2. GEOPHYSICAL APPLICATIONS
On a geological timescale, one million years would be equivalent to one second in human life. However, the evolution of earth did not progress continuously but was often interrupted suddenly by asteroid impacts. Resultant devastating changes in world climate and short-term effects immediately after...