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

324 S. Riad, H. Meyers, and C. KisslingerTable 1. Flinn-Engdahl Seismic Regions Included in the Middle East CatalogNo. Geographical Region No. Geographical Region34 13423433443453463473483493503513523533543553563663673693713723 73374375Iran-USSR Border Region 401Turkmen-Afghanistan Border Region 415Turkey-Iran Border Region 416N.W. Iran-USSR Border Region 417Northwestern Iran 418Iran-Iraq Border Region 419Western Iran 552Iran 553Northwestern Afghanistan 554Southwestern Afghanistan 555Eastern Arabian Peninsula 556Persian Gulf 557Southern Iran 558Western Pakistan 559Gulf of Oman 560Near Coast of West Pakistan 571Turkey 709Turkey-USSR Border Region 710Dodecanese Islands 711Eastern Mediterranean Sea 712CypruB 717Dead Sea Region 718Jordan-Syria Region 720IraqNear Coast of LibyaEastern Gulf of AdenSocotra RegionArabian SeaLaccadive Islands RegionNortheastern SomaliaLibyaUnited Arab RepublicRed SeaWestern Arabian PeninsulaCentral AfricaSudanEthiopiaWestern Gulf of AdenNorthwestern SomaliaSouthern SomaliaAfghanistanPakist anSouthwestern KashmirIndia-Pakistan Border RegionAfghanistan-USSR Border RegionHindu Kush RegionNorthwestern KashmirRouhban, 1983). The total number of earthquakes collected in the first stage wasmore than 22,000. This number was reduced to about 8,000 by limiting the investigationto events of magnitude 2 4.5 or of intensity I, 2 VI. Of these 8,000events, 2,400 were reported as suspected duplicates, and were removed by reviewingthe different sources of data. Preference was given to sources that reevaluatedearthquake parameters and to those including more complete or recent information.After removing the duplicates, reported values of the different parameters for thesame event (e.g., mb, Ms, Mr,, and I,) were used to obtain relations between theseparameters. Magnitudes given without indications of their type were grouped undercatagory M,. They were found to be approximately equal to Ms, but werenot identical. The relations thus obtained were used to assign missing values ofall parameters to the events included in the catalog. According to the obtainedrelations a lower limit of Ms 2 3.9, which is approximately equal to mg 2 4.5 andI, 2 V, was considered for the catalog and the accompanying seismicity map forthe Middle East. A summary of the earthquakes included in the catalog is given inTable 2.2. Magnitude-Magnitude RelationsNormally, magnitudes based on surface and body waves are different for the sameearthquake. This is because mb and Ms sample different parts of the characteristicearthquake spectrum. It has been noted by Gutenberg and Richter (1954) that thedifference between mb and M, is a function of magnitude, and so it follows thatthe magnitude scales based on surface and body waves are not consistent with eachother.