Intensity survey of the Borah Peak, Idaho, earthquake of October 28, 1983

Abstract

Figure 1. A schematic map that shows the locations of the topographic features near to and north of the epicenter. Modified Mercalli intensities (Wood and Neumann, 1931) at the surveyed sites are shown as Roman numerals.

United States earthquakes, 1983

“…Highways in many areas had to be cleared of 58 U.S. Earthquakes, 1983 ID AH 0--Contin ued boulders that had rolled down the slopes. Some homes in Challis, located at the base of large bluffs, were damaged by falling boulders (Reagor and Baldwin, 1984).…”

“…The quake caused water fountains in at least two locations: Near Chilly Buttes and at the upper end of Mackay Reservoir (Reagor and Baldwin, 1984). The fountains lasted only a short time leaving many holes of various sizes and depths.…”

“…Some chimneys in both the residential and business districts were damaged but not as extensively as in Mackay. Reagor and Baldwin (1984) have published detailed descriptions of damage at other communi ties in the epicentral area.…”

“…The throw on the faulting ranged from less than 50 em on the southernmost section to the maximum of 2.55-2.70 m just south of Rock Creek at the western base of Borah Peak (Crone and Machette, 1984). Figure 34 shows the fault scarp about 1 mile south of Doublespring Pass Road (Reagor and Baldwin, 1984). The area in the immediate vicinity of the ground breakage was assigned intensity IX.…”

“…Only a few items fell inside the house. Mackay Reservoir-In their description of the ground effects Reagor and Baldwin (1984) included the following firsthand account of the earthquake by Mr. Anderson, who was fishing at the north end of the reservoir: "I was standing on a gravel sand bar when the earthquake struck (a location about 5 miles southeast of the epicenter). Cracks appeared in the bar and began to gurgle water.…”