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Historical Earthquakes: Personal Comments

Historical Earthquakes: Personal Comments. Willie Lee (Feb. 21, 2011)

isabella-walsh
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Historical Earthquakes: Personal Comments

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  1. Historical Earthquakes: Personal Comments Willie Lee (Feb. 21, 2011) "... old seismograms, if properly interpreted, provide invaluable information on earthquakes in the past, and every effort should be made to save them, regardless of their quality, from possible loss and to make copies in an easily readable form." Hiroo Kanamori (1988)

  2. Some Milestones in Seismology 1880: First effective seismographs (Ewing-Gray-Milne). 1896: BAAS Committee on Seismology (Milne global network). 1901: Geophysical Inst. at Göttingen (Wiechert seismograph). 1903: International Association of Seismology (now IASPEI). 1906: Electromagnetic seismograph developed by Galitzin. 1930s: Benioff seismometers and strain seismograph. 1949: Seismicity of the Earth (Gutenberg & Richter) published. 1963: World-wide Standardized Seis. Network (WWSSN). 1964: International Seismological Centre (ISC). 1970s: Digital era began; Moment tensor inversion; IASPEI/Unesco Historical Seismogram Filming Project. 1991: IRIS Data Management Center.

  3. John Milne (1850-1913): Founding Father of Seismology

  4. Two Seismology Pioneers: Fusakichi Omori (1868-1923), & Emil Wiechert (1861-1928)

  5. Prince Boris Galitzin (1862-1916) and the Galitzin electromagnetic seismograph

  6. Milne Seismogram (at Kew):No damping, low sensitivity, & poor time resolution.Wiechert Seismogram (at Göttingen):Smoked paper records are difficult to scan.

  7. Galitzin and Benioff Seismograms: High sensitivity and photographic recording.Galitzin seismograms: from ~1910, but hard to find;Benioff seismograms: from ~1932

  8. Two Definitions of Historical Earthquakes • Any earthquake occurred from the beginning of the instrumental era (~ 1882) to the beginning of the WWSSN era (~ 1963).  This definition was used in the "Historical Seismogram Filming Project", and in the book "Historical Seismograms and Earthquakes of the World", edited by W. H. K. Lee, H. Meyers, and K. Shimazaki, Academic Press, San Diego, 1988, 513 pp. • Any earthquake occurred before 1900 (or before the first global seismic network around 1900), as used in the Historical Earthquake Catalog Component of the Global Earthquake Model (GEM) initiative ( http://www.globalquakemodel.org/ )

  9. A Modern Earthquake Database for Taiwan? (1) • Any probabilistic seismic hazard analysis (PSHA) requires a reliable database of earthquake source parameters that are derived by modern methods of data processing and analysis using instrumental data (seismic, geodetic, etc.), historical records, and field observations of earthquake effects (intensities from damage, fault ruptures, etc.). • Like in the global case, many Taiwan earthquake catalogs & databases exist, but a reliable and uniform earthquake data-base of Taiwan is not available from 1600 to the present. • There are several compilations of historical earthquakes (before 1900) of Taiwan, but none had used the modern techniques as advocated by E. Guidoboni and J. Ebel, Earthquakes and Tsunamis in the Past: A guide to techniques in historical seismology, Cambridge Univ. Press, 2009.

  10. A Modern Earthquake Database for Taiwan? (2) • In 1898, a Gray-Milne seismograph and an Omori tromometer were established at the Taihoku Meteorological Observatory. • Knowing the distribution and capabilities of seismographic stations in Taiwan and its surrounding regions, it is possible to study Taiwan earthquakes with the following approximate magnitude (M) cutoff: • 1898 – 1903: M > 7.5 Seismographs also at Manila (1884), Osaka (1901), & Zikawei (1903). • 1904 – 1920: M > 6.5 Taiwan local stations & Wiechert seismographs. • 1921 – 1963: M > 6 Galitzin & sensitive seismographs. • 1963 – 1974: M > 5.5 WWSSN stations. • 1975 – 1989: M > 4 .5 Telemetered seismic network at IES. • 1990 – Now: M > 3.5 Digital seismic networks (CWB & IES in Taiwan, GDSN worldwide, etc.)

  11. Difficulties in Studying Historical Earthquakes in Taiwan • Difficulties in collecting and interpreting historical records of Taiwan earthquakes before 1900. • Collecting seismograms and time/amplitude/period data for Taiwan earthquakes from 1900 to 1962 will be costly. • Locating earthquakes before 1963 is difficult because station distribution is often poor, seismographs are not standardized, and station clocks often have large errors. Grid-search location software helps, but requires judgments. • Computing uniform earthquake magnitudes is a challenge. • Waveform modeling helps in constraining source location, focal mechanism & quake size, but requires a lot of work.

  12. Studying Historical Quakes: Some Resources • The SeismoArchives website: http://www.iris.edu/seismo/ contains scanned seismograms, station information, and some useful books and papers. • Frechet, J., M. Meghraoui, and M. Stucchi (Editors) (2008). Historical Seismology: Interdisciplinary studies of past and recent earthquakes. Springer, Berlin. • Kanamori, H., L. Rivera, and W.H.K. Lee (2010). Historical seismograms for unravelling a mysterious earthquake: The 1907 Sumatra Earthquake. Geophys. J. Int., 183, 358-374. http://www.gps.caltech.edu/people/kanamori/publications • Lee, W.H.K., H. Meyers, and K. Shimazaki (Editors) (1988). Historical Seismograms and Earthquakes of the World, Academic Press, San Diego. Free download at: http://www.iris.edu/seismo/info/publications/Lee1988.pdf

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