Intensity distribution and isoseismal maps for the Northridge, California, earthquake of January 17, 1994

Dewey, James W.; Reagor, B.G.; Dengler, Lori; Moley, Kathy

doi:10.3133/ofr9592

Cited by 54 publications

(21 citation statements)

References 2 publications

(7 reference statements)

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“…In each block, the number of red-tagged buildings, N, and the number of breaks in water pipes were counted. Also each block was assigned a value of horizontal peak ground velocity, v max , and intensity of shaking, I MM , using the smoothed contour maps in and in Dewey et al (1994).…”

Section: Density Of Red-tagged Buildings As Function Of V Max or I Mmmentioning

confidence: 99%

“…To study possible departures from the ''smoothed'' maps of v max (shown in Fig. 2), and I MM (Dewey et al 1994), the ''new'' estimates of v max and I MM were calculated for all 1 km 2 blocks with N Ն 1 and n Ն 0. For sites with N = 0, the original estimates of v max and I MM were kept.…”

Section: Inferences On V Max and I Mm From Data On N And Nmentioning

confidence: 99%

“…By the total number, density, and location of recording stations (relative to the causative fault), this has been by far the best recorded earthquake, and it was possible to draw smoothed contour maps of peak amplitudes and response spectrum amplitudes of ground motion Todorovska and Trifunac 1997a,b). Smoothed contour maps of modified Mercalli intensity were prepared based on felt reports of the shaking at selected locations (Dewey et al 1994). However, neither the density of strong motion stations nor the density of sites used by Dewey et al (1994) were sufficient to help in interpretation of the concentrated patterns and spatial fluctuations of observed strong motion effects (Gao et al 1996;Spudich et al 1996) and of the observed damage (Stewart et al 1994).…”

Section: Introductionmentioning

confidence: 99%

“…Smoothed contour maps of modified Mercalli intensity were prepared based on felt reports of the shaking at selected locations (Dewey et al 1994). However, neither the density of strong motion stations nor the density of sites used by Dewey et al (1994) were sufficient to help in interpretation of the concentrated patterns and spatial fluctuations of observed strong motion effects (Gao et al 1996;Spudich et al 1996) and of the observed damage (Stewart et al 1994). The smoothed contour maps could be used to find only the average overall trends of the degree of damage as a function of the level of ground shaking (Trifunac and Todorovska 1997a,b).…”

Section: Introductionmentioning

confidence: 99%

“…Such relationships were presented by Trifunac and Todorovska (1997a,b) for the number of red-tagged buildings per km 2 , N (mostly wood-frame structures), and for the number of breaks in water pipes per km 2 , n, based on damage and ground motion data in typical residential neighborhoods of San Fernando Valley and Los Angeles, following the Northridge earthquake. They used data on tagged buildings and breaks in water pipes (gathered by City of Los Angeles Department of Building Safety and Department of Water and Power) (Stewart et al 1994), smoothed contour maps of horizontal peak ground velocity and peak strain factors presented by and a modified Mercalli intensity map prepared by Dewey et al (1994). Trifunac and Todorovska (1997a,b) analyzed the data sets on red-tagged buildings and on breaks in water pipes independently of each other.…”

Section: Introductionmentioning

confidence: 99%

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Reduction of Structural Damage by Nonlinear Soil Response

Trifunac

Todorovska

1999

J. Struct. Eng.

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Following the 1994 Northridge earthquake, the areas with a high density of reported breaks in water pipes in typical residential areas in San Fernando Valley and in Los Angeles often did not coincide with the areas having a high density of severely damaged (red-tagged) buildings. As the former is an indicator of large strains and nonlinear soil response, this observation suggests that the damage to buildings in some areas may have been smaller than expected because the soil dissipated part of the energy of the ground motion by nonlinear response. This paper presents an attempt to quantify this relationship between the density of red-tagged buildings, N (per km 2), and the severity of shaking (via peak horizontal ground velocity, v max , or modified Mercalli intensity, I MM), including the density of breaks in water pipes, n (per km 2), as a variable specifying the level of strain in the soil. Approximate empirical relationships for N = f(v max , n) and N = f(I MM , n) are presented. The trends in the data indicate that, for v max in the range from ϳ35 to ϳ125 cm/s, the rate of growth of N versus v max tends to decrease at sites with large strain in the soil (i.e., large n). For v max beyond ϳ150 cm/s, the beneficial effects of nonlinear soil response seem to fade out, as large differential motions associated with soil failure begin to contribute to the damage of structures. Assuming fairly uniform density and quality of building stock and of water pipes in the areas studied, the derived relationships are then used to map v max and I MM in San Fernando Valley and in Los Angeles. The resulting maps are more detailed than what could be obtained from the density of strong motion stations and of sites with reports on felt intensity.

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Section: Density Of Red-tagged Buildings As Function Of V Max or I Mmmentioning

confidence: 99%

Section: Inferences On V Max and I Mm From Data On N And Nmentioning

confidence: 99%