3. - usaid

Technical Description
August 31, 1968, Earthquake : 7.3 on the Richter magnitude scale; 10 on the
Mercali intensity scale. Its focal depth was estimated at 13 kilometers.
Epicenter - 33.97 degrees north; 59.02 degrees east or about 20 kilometers
east of Dasht-e-Biaz . It struck an area of 4,500 square kilometers in the
eastern Iran province of Khorassan, 901 kilometers east southeast of
Tehran. Directly within the energy release areas were the towns of Kakh,
Gonabad, Dasht-e-Biaz, and numerous villages and hamlets dotting the Byaz
foothills.
September 1, 1968, Earthquake: 6.3 on the Richter magnitude scale; 9 to 10
on the Mercali intensity scale. Epicenter 34.04 degrees north and 58.22
degrees east. Its focal depth was given as 15 kilometers. Great physical
damage to the town of Ferdows and the surrounding areas, 90 kilometers west
of the epicenter for the August 31 temblor.
Field observations by U. S. geologists and other scientists noted that the
primary effect of the earthquakes was a "zone of faulting that developed
across an alluvial plain trending westerly for about 20 miles." Surface
fault lines were observed running.east-west from Dasht-e-Biaz. The UNESCO
seismology team reported the fracture in the earth's crust as being 70
kilometers long and the focal point for the origin of the earthquake
waves was measured as 10 kilometers deep, with surface fracture passing
through Dasht-e-Biaz, Kakh, Moin, and Moghri. Observations along the fault
zone showed that the north side moved westward relative to the south side.
The maximum displacement occurred between Moin and Dasht-e-Biaz.
Mr. David J. Leeds, geophysical consultant for the Los fkgeles, California
firm of Dames & Moore, Middle East, in reporting on the intensity stated:
"An east-west oval area, with a long axis of about 125 kilometers of
'complete' destruction of Iranian mud block houses exists. Villages in
this area have every house damaged beyond use or repair. The fault is
within this area, One village, Dasht-e-Biaz, just 300 yards north of the
fault line, was shaken absolutely level. No structural element of a
building remained identifiable--no arches or walls, just lumps of mud."
John A. Reinemund, Chief, Branch of Foreign Geology, U. S. Geological
Survey, Department of Interior,,made the following comments on geologic
factors: "The iqortance of geologic factors can be observed in the damaged
villages. The incredible destruction of Dasht-e-Biaz is related not only
to its proximity to the fault along which the earthquake was generated, but
also to the fact that it was built on low-lying, terraced alluvium with
depth to water table generally less than 15 feet. Damages in Kakh appear
greater to low-lying houses than to buildings on higher ground underlain
by old alluvium and with a deeper water table. Some villages near Kakh
located on bedrock received relatively little damage. Where possible,
villages should be relocated away from this and other faults known or
suspected to be active and should be placed on bedrock or on hi@ ground
having a low water table. Geologic mapping is needed to identify these