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)

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

IASPEI/Unesco Historical Seismogram Filming Project.IASPEI/Unesco Historical Seismogram Filming Project. 1991: IRIS Data Management Center.1991: IRIS Data Management Center.

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

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

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

Milne Seismogram (at Kew):Milne Seismogram (at Kew): No damping, low sensitivity, & poor time resolution.No damping, low sensitivity, & poor time resolution.

Wiechert Seismogram (at Göttingen):Wiechert Seismogram (at Göttingen): Smoked paper records are difficult to scan.Smoked paper records are difficult to scan.

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

Benioff seismograms: from ~1932Benioff seismograms: from ~1932

Two Definitions of Historical EarthquakesTwo 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/ )

A Modern Earthquake Database for Taiwan? (1)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.

A Modern Earthquake Database for Taiwan? (2)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.)

Difficulties in Studying Historical Earthquakes Difficulties in Studying Historical Earthquakes in Taiwanin 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.

Studying Historical Quakes: Some Resources 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