Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

Analysis of Historical Seismograms of Large Mexican Earthquakes832CPACIFICl!120"WI I I 1k.,,Figure 13. Tectonic setting of the Jalisco region. The boundary between Riveraand COCOS plate is uncertain; the solid line (marked R) and dashed line (marked EM)are the boundaries inferred by Reid (1976) and Eissler and McNally (1984), respectively.Stations used in the analysis are shown by solid triangles. The numbers associated withthe locations of the aftershocks are in chronological order. The dashed contour is the totalestimated aftershock area of the 3 June and 18 June, 1932 earthquakes. A dashed linedivides this area; the NW and the SE parts roughly outline 3 June and 18 June aftershockareas, respectively. Shaded region is the early aftershock area (3 to 8 June) estimatedfrom GUM and TAC. Aftershock area of 1973 Colima earthquake is taken from Reyeset al. (1979).had only concentrated on the analysis of modern seismograms. While all historicalseismograms axe useful, the observatories which have been in continuous operationand have kept operating the old seismographs, in spite of many inconveniences,provide the most valuable data. Old and new seismograms from such observatoriescan then be directly compared and meaningful and reliable conclusions can bereached regarding older earthquakes.ACKNOWLEDGEMENTSThe review is biased; only the results of the analysis in which the author participatedare emphasized. The author thanks his many colleagues. Acknowledgementis made to the seismic observatories of Uppsala, DeBilt, Giittingen, Stuttgart, Strasbourg,Copenhagen, and La Paz for making available copies of seismograms. Partof this research was funded by Consejo Nacional de Ciencias y Tecnologia (CONA-CYT) of Mexico.