Mary Lou Zoback

U.S. Geological Survey

The 1906 Earthquake – lessons learned, lessons forgotten, and future directions

At the beginning of the 20th century, San Francisco was the “most cosmopolitan city outside of New York”. Overnight, everything changed when the city was violently shaken awake at 5:12 AM on April 18, 1906.  The 1906 earthquake and resulting firestorm over the next 3 days left San Francisco devastated and significant damage throughout northern California. More than 3000 persons lost their lives and in San Francisco alone, 225,000 of the city’s 400,000 citizens were left homeless.  The centennial of this major natural disaster affords an opportunity to commemorate the cultural and social response to this historic event and to highlight a century of progress in understanding earthquake hazards and reducing the risks they pose.

The 1906 magnitude 7.9 earthquake on the northern San Andreas Fault marked the birth of modern earthquake science.  For the first time, the effects and impacts of a major seismic event were systematically investigated and documented in a detailed report published in 1908.  These investigators not only carefully mapped the entire 200-mile-long onshore fault rupture, but they also followed and mapped the fault south to the Mexican border, documenting the San Andreas as a major through-going geologic structure for the first time. Their surveys of damage to structures concluded that destruction was closely related to building design and construction--a painful lesson oft repeated around the world. 

Perhaps the most important scientific result to come out of the 1906 earthquake was the concept of an earthquake cycle, the “elastic rebound hypothesis”-- that earthquakes represent sudden release of elastic energy along a fault resulting from a cycle of slow strain accumulation produced by relative displacements of neighboring portions of the crust. This concept is still accepted today with minor modifications, even though the basis for large-scale horizontal displacements was not established until the plate tectonic revolution six decades later.

As earthquake science evolves, reanalysis of the 1906 earthquake data continues to yield new insights about that event and the behavior of large strike-slip faults in general. Looking to the future, a dense array of continuous GPS recorders in N. California, part of the National Science Foundation’s EarthScope’s Plate Boundary Observatory, can search for fault interactions and determine if an acceleration of strain rate precedes the next big earthquake as it may have prior to 1906.

About Dr. Zoback

Mary Lou Zoback


Ph.D., Stanford University, Geophysics, 1978
B.S., Stanford University, Geophysics, 1974

Positions Held

Senior Research Scientist, USGS, 2002-
Chief Scientist, USGS, Western Hazards team, 1999-2002
Research Geophysicist, USGS, Earthquake Hazards Program, 1979-1999
National Research Council Postdoctoral Fellowship, USGS, 1978-1979

Mary Lou Zoback is a Senior Research Scientist with the United States Geological Survey, Menlo Park, CA and currently serves as the Regional Coordinator for the USGS Northern California Earthquake Hazard Program. She is a respected geophysicist recognized for her work on the relationship between earthquakes and state of stress in the Earth's crust.  From 1986-1992 Dr. Zoback created and lead the World Stress Map project, an effort that actively involved 40 scientists from 30 different countries. This work demonstrated that broad regions of the earth's crust in the interior of tectonic plates are subjected to relatively uniform stresses that result from the same forces that cause plate motion.  These results imply that earthquakes in the interior of continents result from the same causative forces as those occurring on plate boundaries, but are the result of much slower processes.

Dr. Zoback has served on numerous national committees and panels on topics ranging from continental dynamics, storage of high-level radioactive waste, the role of “inquiry” in the National Science Education Standards, and facilitating interdisciplinary research. She is currently a member of the executive committee for a National Research Council study on “Earth Science and Applications from Space” which is defining a scientific strategy and rationale for the next generation of earth observations from space in conjunction with land-based monitoring.  She previously served on NASA’s Solid Earth Sciences Working Group.  Their report, “Living on a Restless Earth”, developed a long-term vision with the goal of understanding natural and perturbed earth systems well enough to predict outcomes, consequences and impacts.

Dr. Zoback is active in several professional societies.  She is a past-President of the Geological Society of America and formerly served as President of the Tectonophysics Section of the American Geophysical Union and as a member of the AGU Council. In 1987 Zoback was awarded the American Geophysical Union's Macelwane Award for "significant contributions to the geophysical sciences by a young scientist of outstanding ability". In 1995 she was elected into the National Academy of Sciences.

Selected Publications

Zoback, M. L., and Zoback, M. D., 1980, State of stress in the conterminous United States: Jour. Geophys. Res., v. 85, no. B11, p. 6113-6156.

Zoback, M. L., Anderson, R. E., and Thompson, G. A., 1981, Cenozoic evolution of the state of stress and style of Tectonism of the Basin and Range Province of the western United States: Phil. Trans. Roy. Soc. London A, v. 300, p. 407-434.

Zoback, M. D., and Zoback, M. L., 1981,  State of stress and intra-plate earthquakes in the central and eastern United States:  Science, v. 213, p. 96-104.

Zoback, M. D., Zoback, M. L., Mount, V. S., Suppe, J., Eaton, J. P., Healy, J. H., Oppenheimer, D., Reasenberg, P., Jones, L., Raleigh, C. B., Wong, I. G., Scotti, O., Wentworth, C., 1987, New evidence on the state of stress on the San Andreas fault system:  Science, v. 238, p. 1105-1111.

Zoback, M. L., and Zoback, M. D., 1989, Regional tectonic stress field of the continental U.S.:  Geophysical Framework of the Continental U.S., L. Pakiser and W. D. Mooney, eds., Geological Society of America Memoir, 172, p. 523-539.

Zoback, M. L., Zoback, M. D., Adams, J. A., (23 authors total), 1989, Global patterns of tectonic stress:  Nature, v. 341, p. 291-298.

Zoback, M. L., 1992, First and second order patterns of stress in the lithosphere:  the World Stress Map project:  Journal Geophysical Research, v. 97, p. 11703-11728.

Zoback, M. L., 1992, Stress field constraints on intraplate seismicity in Eastern North America:  Journal Geophysical Research, v. 97, p. 11761-11782.

Zoback, M. L., Jachens, R. C., and Olson, J. A., 1999, Abrupt along-strike change in tectonic style:  San Andreas fault zone, San Francisco Peninsula: Journal of Geophysical Research:  v. 104, p.10719-10,742.

Committee on Development of an Addendum to the National Science Education Standards on Scientific Inquiry, 2000, Inquiry and the National Science Education Standards, National Academy Press, 202 p.

Geist, E. R., and Zoback, M. L., 2000, Analysis of the tsunamis generated by the Mw7.8 1906 San Francisco earthquake:  Geology, v. 27, p. 15-18.

Zoback, M.L., 2001, Grand challenges in earth and environmental sciences:  science, stewardship, and service for the 21st century:  GSA Today, v., p.41-46.