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

The U. S. Geological Survey's Databases of Seismic Events145(a)LOCAL - REGIONAL DATABASESDATE TIME LAT LONG DEPTH MAG N GAP DMlN RMS TW PL ERH1 TW PL ERHZ ML MD El72 0 PM NS2 5 B S 0790228 2'27072 60N385 141W359 127 71 20 66 60 42 0 0 13 90 0 13(b)GLOBAL DATABASEAGENCY DATE TIME R LAT LOhG DEPTH NP RMS mb US ZH MAG MAG INT EFFECTS IDE F-ECS 49790228 212767200 60 642 -141 598 12 7 6 7 12 6 90MLPMR 7 52hmGS 7 D TS X 19N C P20(c)NATIONAL DATABASE(PRIMARY FILE)DATE TIME UNC S REF PR ID L F-E GRID LAT LCN C N UNC REF DEPTH R UNC NP919790228 2127072 2 0 5 GS 1 AK 19 60 6417 -141 5985 20 0 05 GS 12 7 10 0 0REFGSTYPE MAG U4c RMS N REF TYPE MAG UNC RUS N REF ZH W PU TO TE UP u) BINARY FLAGS BINARY FLAGSmb 6 2 0 3 99 ISC MI 0 3 ISC 2 4 2 3 1 21 23 100000001100100 000000000000tllI(SECONDARY FILE HYPOCENTEP SlATlSTlCS)DATE TIME ERH' AZ1 PI ERHZ A22 PZ ERZ A23 P3 Rus GAP WIN NF CO UFAC CCC NS919790228 2127072 I 3 0 0 1 3 90 0 2 5 0 90 0 42 66 60 68 B 0(SECONOARY FILE ADDITIONAL MAGN TUDES)DATE TIME TYPE MAG UNC RMS N REF TYPE UAG UNC Rus N REF TYPE MAG UNC RMS N REF919790228 2127072 ML 6 9 0 5 PMW Ur 7 52 0 1 627(SECONDARY FILE INTENSI-Y 3ATA)>ATE TIME INT E UNC C REF AREA919790228 2127072 7 D 1 0 622 5000(00)Figure 1. Internal formats of three US. Geological Survey seismic event databases forthe St. Elias, Alaska, earthquake on 28 February 1979 at 21:27::07.2 UTC. For clarity, theformats have been expanded by adding one or two blank spaces between the parameters.The national database contains all of the parameters in the local-regional and globaldatabases, plus additional counters, control characters, uncertainty estimates, references,and secondary files when needed. The symbols are abbreviated parameter labels, whichare explained in the user manuals for each database.4. Database DevelopmentThe USGS database files go through as many as five developmental stages inwhich the data are collected, verified, corrected, merged, and prioritized. Theprincipal sources from which the data were collected are shown in Figure 3. Thesources include numerous regional catalogs and even a few global catalogs of historicalearthquakes that had been published before instrumental seismology was wellestablished (for example, see Milne, 1911). Other sources include monthly weatherreports (1874-1924) of the U.S. Army Signal Corps, reports of explorers and mappingexpeditions, private journals, and early newspaper articles. Data from thesesources for the more significant felt or damaging earthquakes in the United Statesand its territories were assembled and published in Earthquake History of the UnitedStates (latest revision by Coffman, von Hake, and Stover, 1982). Abstracts of EarthquakeReports for the Pacific Coast and the Western Mountain Region (1932-1973)and United States Earthquakes (1928-current), respectively issued quarterly andannually by the U.S. Coast and Geodetic Survey and successor organizations, areimportant sources of information on felt or damaging earthquakes in the UnitedStates.The USGS national and global databases contain calculated and computed hypocenterparameters from several published sources. The monthly bulletin (1913-1917)of the Seismological Committee, British Association for the Advancement of Science,is the earliest source of the calculated hypocenter parameters in the databases.These data continued to be published (covering 1918-1963) in the International SeismologicalSummary (ISS), enhanced by the development of improved travel times(Jeffreys and Bullen, 1940) that are still used throughout the world. The monthly