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

The Historical Seismograms of Colombia 473Colombian Coffee Planters and the Division of Salinas of the Bank of the Republic,became interested in helping the aims of the Institute Director. With their financialsupport, installation of two seismic stations, one in Chinchini (4” 58’ N, 75’ 37’W, elevation 1,360 m), and other in Galerazamba (lO”47’08” N, 75” 15‘44” W,elevation 21 m), was approved in 1945.The new stations began operation at Galerazamba on April and at Chinchinii onAugust of 1949, and since that time, they were kept in operation until the end of thisperiod. The instruments of both stations were similar: photographic seismographsfrom Sprengnether and galvanometers from Leeds & Northrup of Philadelphia; oneshort-period vertical-component of the DM type and two horizontal components ofthe H type; the short period was 1.5 seconds and the long period was 16 seconds.The equipment was completed with a triple drum, one electric clock from the StandardTime Clock Co., and one transmitting and receiving radio. The orientation ofthe components was N-S and E-W; other constants could be determined; however,they were not taken into account for parameters determination. Time correctionwas taken from the international WWV time station and automatically marked onthe records. The drums rotation was kept at 0.5 mm/sec, and the spacing betweenthe lines at 5 mm. The recording photographic paper was of standard size: 30 cmin width and 90 cm in length.Both stations were kept functioning until 1960 and onwards with three components,and therefore, the quantity of records are about 4,000 each, for a total of 8,000during this period. However, the useful records from Galerazamba are appreciablyless, because the interference of sea waves in this station is too great.The seismograms of both stations have been analyzed with those from Bogotdand their data published in the same Bulletins.As a final note, it should be mentioned here that in 1957, a new seismic station wasestablished in F‘uquene Island, about 100 km to the north of Bogotd, to cooperatein the investigations of the International Geophysical Year. The seismograph usedwas a photographic vertical component with a period of 6 sec, Galitzin-Wilip type,made by the Askania workshop.REFERENCESTurner, H. H. (1922). On the arrival of earthquake waves at the antipodes, and the measurementof the focal depth of an earthquake, Mon. Not. Roy. Astron. SOC. Geophys.Suppl., 1, 1-13. (also see International Seismological Summary, 1921 and 1922).Inglada Y Ors, Vicente (1943). Contribucibn a1 Estudio del Batisismo Suramericano de 17de ener de 1922, Inst. Geogr. y Catast. - Memorias del I.G.y C., Tom0 16, 8, Madrid.