Leon Knopoff

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Leon Knopoff (born July 1, 1925 in Los Angeles , † January 20, 2011 in Sherman Oaks ) was an American geophysicist . He was considered one of the fathers of theoretical seismology.

biography

After attending school, he first studied electrical engineering at the California Institute of Technology (CALTECH) and graduated in 1944. He then completed postgraduate studies in physics at CALTECH, which he completed in 1949 with a doctoral thesis.

He then spent two years at Miami University and then became a research assistant at the University of California, Los Angeles (UCLA), where he became an associate professor in 1957 and was given a full professorship in geophysics in 1959 . In 1956 he drafted a first representational theorem for a complete seismic wave equation and also presented important work in the field of seismic wave diffraction , for example in relation to the Earth's core .

In 1961 he was appointed professor of physics there. In 1964 he published with Robert Burridge the representation theorem of Burridge and Knopoff, which forms an important basis of theoretical seismology. In 1967 he created the basis for the computer simulation of seismicity on geological faults with the Burridge-Knopoff model. In this model, the points on the fault are simulated by masses that are held by spring forces and are connected to each other and are subject to a frictional force. He used it to simulate earthquakes both on the computer and in physical models (slider model). One result of the research was that earthquakes tend to occur in clusters.

Between 1972 and 1986 he was also Associate Director of the Institute of Geophysics and Planetary Physics (IGPP) at UCLA. In 1980 he described a universal statistical power law (i.e. a fractal distribution) for the spatial distribution of earthquakes , which have consequences for the geometry of earthquakes at faults. He also extensively examined the statistics of the temporal sequence of foreshocks of larger earthquakes with the aim of developing a forecast method. However, Knopoff also demonstrated that most small earthquakes were not foreshocks that preceded the large quakes, but rather signs of stress relief.

He also examined the relationship between earth tides and earthquakes. In 1964, he concluded that there was no connection. In 1983 he investigated the problem again together with the astronomer Steven Kilston, this time on a regional level in California (due to the special north-south orientation of the San Andreas Fault) and only for strong earthquakes and found connections (for example, the earthquakes mostly occurred when full - and new moon on and at sunrise and sunset). You predicted stronger quakes in the Imperial Valley of California in 1987 in your Nature article, and two occurred.

He also dealt with determining the speed of seismic waves, measuring the earth's tides at the South Pole, determining the age of ceramics with thermoluminescence dating and musicological issues (he researched from 1960 at the Institute for Ethnomusicology at UCLA, published works with William Hutchinson on psychophysical aspects of music and played piano and harpsichord himself).

Knopoff published over 350 papers and had 38 PhD students at UCLA.

For his work he received the Emil Wiechert Medal of the German Geophysical Society in 1978 and the gold medal of the Royal Astronomical Society in 1979 . In 1990 he received the Medal of the Seismological Society of America. From 1972 to 1974 he was on the Earthquake Council of the Governor of California.

He was a member of the National Academy of Sciences (1963), the American Association for the Advancement of Science , the American Philosophical Society, and the American Academy of Arts and Sciences (1965). He was an honorary doctorate from the University of Strasbourg (2004) and an honorary professor at the Institute of Geophysics of the China Earthquake Administration (2004). He has been visiting China since the 1970s.

Even after his retirement , Knopoff continued to work and, among other things, was an author for the journal “ Nature ”. From 1985 to 1990 he was on the editorial board of Science magazine .

A chair at UCLA is named after him and his wife Joanne VC Knopoff, both donated to the university in 2001 with a donation of $ 500,000.

Publications

literature

swell

Individual evidence

  1. ↑ a b Thomas H. Maugh II: Leon Knopoff dies at 85; UCLA scientist who applied computer modeling in earthquake research. In: Los Angeles Times. February 3, 2011, accessed October 9, 2018 .
  2. ^ F. Gilbert, Knopoff Diffraction of elastic waves in the core of the earth , Bull. Seism. Soc. America, Vol. 51, 1961, pp. 35-49
  3. ^ Burridge, Knopoff Body-force equivalents for seismic dislocations , Bulletin Seismological Society of America, Volume 54, 1964, pp. 1875-1888
  4. ^ Burridge-Knopoff model at Math World . Burridge, Knopoff, Bull. Seis. Soc. Amer., Vol. 57, 1967, p. 341
  5. ↑ Regardless of the strength of the earthquake and the extent of the area under consideration. However, the power law showed differences for shallow (drop with a power of about 1.0) and deep tremors (drop with a power of 1.5).
  6. ^ YY Kagan, Knopoff Spatial distribution of earthquakes: the two-point correlation function , Geophysical Journal, Volume 62, 1980, pp. 303-320, abstract
  7. ↑ Kagan, Knopoff Statistical Short Term Earthquake Prediction , Science, Volume 263, 1987, pp. 1563-1567. Abstract
  8. ↑ Knopoff Earth tides as triggering elements of earth quakes , Bull. Seismolog. Society America, Vol. 54, 1964, pp. 1865-1870, abstract
  9. ^ Kilston, Knopoff Lunar-solar periodicities of large earth quakes in southern California , Nature, Volume 303, 1983, p. 21. Los Angeles Times, April 6, 1986 . Relationships between the arrangements of sun-moon-earth have also been known in moonquakes since the Apollo missions.
  10. ↑ Due to a constellation in the 18-year periodicity of the lunar orbit
  11. ↑ http://www.nature.com/nature/debates/earthquake/profiles.html
personal data
SURNAME Knopoff, Leon
BRIEF DESCRIPTION American geophysicist and geologist
DATE OF BIRTH July 1, 1925
PLACE OF BIRTH los Angeles
DATE OF DEATH January 20, 2011
Place of death Sherman Oaks