222 Seismology

61 Route 9W - PO Box 1000

Palisades

NY

10964-8000

US

Phone: 

(845) 365-8389

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I have worked at Columbia since 1971, with a couple of years on leave in Washington working on nuclear arms control (in the U.S. Department of State), and sabbaticals in New Zealand, California (Livermore) and New Mexico (Los Alamos). I started out in research with a mathematics background, and an interest primarily in the theory of seismic wave propagation and in methods to understand how the recorded shapes of seismic waves are affected by processes of diffraction, attenuation and scattering. From such scientific work we learn details of the Earth's internal structure, and details of fault motion in earthquakes as rock spontaneously fractures and moves to reduce stress. Since the mid-1980s my work has focused on the use of seismological methods to study underground nuclear explosions and their implications in both the scientific and political worlds. There have been about 2, 000 such explosions (about one a week for about forty years, with few since 1990). How they are detected, identified and located - and how big they are - are subjects of debate in technical and scientific forums. These issues are critical in evaluating present or prospective arms-control treaties. A side effect of the end of the Cold War has been new opportunities to acquire seismic data on earthquakes and explosions in Russia and Central Asia. Together with my colleague Won-Young Kim at Lamont, I have had joint projects since 1991 with scientists working in Russia and Kazakhstan. Beginning in 2004, I have been teaching a general course for undergraduates on "Weapons of Mass Destruction."

There is ongoing discussion of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and the associated Non-Proliferation Treaty (NPT). The CTBT has been signed by over 160 countries, and the NPT by over 180. At the CTBT negotiations in Geneva in 1994, I formally presented an "expert's paper" for the United States, on monitoring issues associated with this treaty. Starting in summer 2000 I worked on a National Academy of Sciences panel that in July 31 2002 issued a detailed report on "Technical Issues Related to the Comprehensive Nuclear Test-Ban Treaty." From 2000 to 2003, I led 15 people in an applied research project to improve the accuracy with which seismic events (earthquakes, explosions) are routinely located in East Asia by organizations engaged in treaty monitoring. Since 2003 I have worked with others at Lamont on the wider application of modern methods of event location, using waveform cross-correlation on a massic scale and locating numerous events all at the same time. Copies of my recent papers may be downloaded from the "long cv" section of my personal web pages (see URL given above).

I retain a strong interest in the scientific study of seismic signals, and in 1996, together with Xiaodong Song, discovered seismological evidence that the inner core of the Earth is rotating eastwards with respect to the mantle and crust. During the years 2000 to 2005, working with Anyi Li and Jian Zhang, we found even stronger evidence. In 2005, Xiaodong and I, together with four of our grad students, published another paper on inner core rotation, that had data a hundred times better than our 1996 paper, and obtained essentially the same result: seismic waves through the inner core on a path from the South Sandwich Islands to Alaska have a travel time that gets smaller by about a tenth of a second per decade. In July 2002, the second edition of my textbook "Quantitative Seismology" (originally written with Kei Aki in the 1970s) was published after seven years of rewriting. I maintain associated web pages on the Aki/Richards second edition. Outside my office, and outside my home, I am a member of the Council on Foreign Relations, an organist, sing in the choir of Grace Episcopal Church, Nyack, NY, sail small boats...

Some of my projects:

• Lamont Consortium to Improve the Location Estimates of Seismic Events in East Asia ( details )
• Earth's Inner Core --- Discoveries and Conjectures ( details )
• Quantitative Seismology, second edition ( details )
• Technical Issues Related to the Comprehensive Nuclear Test Ban Treaty ( details )
• Evaluation of Cross-Correlation Methods on a Massive Scale for Accurate Relocation of Seismic Events(details )