Dr. Cliff Frohlich

University of Texas at Austin

Deep Earthquakes and the Secrets of Seismology

About a quarter of all earthquakes originate at depths more than 60 km (40 miles) beneath the Earth’s surface, and some at depths as great as 700 km (440 miles). Since their discovery in 1927, these ‘deep’ earthquakes have been an enigma because pressures and temperatures are too great at these depths for ordinary brittle fracture to occur. Deep earthquakes pose a serious hazard in a few parts of the world, including Romania, parts of South America, and (possibly) in the northwestern United States. Dr. Frohlich’s talk will address what is known and unknown today about the mechanical origin of deep earthquakes and explain why they have been used disproportionately in studies of the Earth’s interior structure. Frohlich will use familiar items to illustrate Earth structure and explain many principles of earthquake mechanics. Seismology as presented by Frohlich will involve raw and cooked eggs, baseballs, coffee pots, champagne bottles, diamonds, air hockey, and ultrasound. In every profession there are ‘secrets’, that is, basic information that is known to all who practice the profession but somehow unknown or misunderstood by the public. For example, most people are unaware that seismologists most often focus on understanding earth structure rather than investigating the properties of earthquakes themselves. All who attend Frohlich’s lecture, young and old, will learn a great deal about basic earthquake seismology, including much that all seismologists know but seldom tell.

About Dr. Frohlich

Cliff Frohlich


Ph.D., M.S., Cornell University (1976, 1973)
B.A., Grinnell College (1969)

Positions Held

Associate Director, Senior Research Scientist, University of Texas Institute for Geophysics (1978-present)

Dr. Cliff Frohlich was born in Wisconsin, grew up in Ohio, South Dakota, and Maryland, then attended Grinnell College in Iowa, where he received a B.A. in Mathematics and Physics, and graduate school in New York, where he received a Ph.D. in Physics. Since 1978 he has been a researcher at the University of Texas Institute for Geophysics, where he now serves as Associate Director.

Dr. Frohlich’s two most persistent research interests concern deep earthquakes and the statistical analysis of earthquake catalogs. However, his focus regularly wanders: earlier in his career he participated in field projects in Alaska and Vanuatu involving the deployment of ocean bottom seismographs; currently he is investigating moonquakes and tsunamis. He has published two books and about 100 research papers, most concerning earthquake seismology, but several on the physics of sports.


Frohlich, C. Deep Earthquakes, Cambridge University Press, Cambridge, U. K., 574 pp., 2006.

Frohlich, C., and S. D. Davis. Texas Earthquakes, University of Texas Press, Austin, Texas, 275 pp., 2002.

Selected Publications

Frohlich, C. and L. R. Wetzel. Comparison of seismic moment release rates along different types of plate boundaries, Geophysical Journal International, (in press), 2007.

Frohlich, C. and Y. Nakamura. Possible extra-Solar-System cause for certain lunar seismic events, Icarus, 185, 21-28 2006.

Frohlich, C. What makes bowling balls hook? American Journal of Physics, 72, 1170-1177, 2004.

Frohlich, C. Display and and quantitative assessment of distributions of earthquake focal mechanisms, Geophysical Journal International, 144, 300-308, 2001.

Frohlich, C. and S. D. Davis. How well constrained are well-constrained T, B, and P axes in moment tensor catalogs? Journal of Geophysical Research, 104, 4901-4910, 1999.

Frohlich, C. Cliff's nodes concerning plotting nodal lines for P, SH, and SV, Seismological Research Letters, 67, 16-24, 1996.

Frohlich, C., K. Kadinsky-Cade, and S. D. Davis. A reexamination of the Bucaramanga, Colombia, earthquake nest, Bull. Seismol. Soc. Amer., 85, 1622- 1634, 1995.

Frohlich, C. Baseball: Pitching no-hitters, Chance, 7(3), 24-30, 1994. Reprinted in Anthology of Statistics in Sports, edited by J. Albert, J. Bennett and J. J. Cochran, Society for Industrial and Applied Mathematics, Philadelphia, PA, 103- 109, 2005.

Frohlich, C. Earthquakes with non-double-couple mechanisms, Science, 264, 804-809, 1994.

Frohlich, C. and S. D. Davis. Teleseismic b values; Or, much ado about 1.0, Journal of Geophysical Research, 98, 641-644, 1993.

Frohlich, C. Deep earthquakes, Scientific American, 260(1), 48-55, 1989.

Frohlich, C. Aerodynamic drag crisis and its possible effect on the flight of baseballs, American Journal of Physics, 52, 325-334, 1984.

Buskirk, R. E., C. Frohlich and G. V. Latham. Unusual animal behavior before earthquakes: a review of possible sensory mechanisms, Reviews of Geophysics and Space Physics, 19, 247-270, 1981.

Frohlich, C. The physics of somersaulting and twisting, Scientific American, 242(3), 154-164, 1980.