Chimney Damage in the Greater Seattle Area from the Nisqually Earthquake of 28 February 2001

Abstract

Unreinforced brick chimneys in the greater Seattle area were damaged repeatedly in the Benioff zone earthquakes of 1949, 1965, and 2001. A survey of visible chimney damage after the 28 February 2001 Nisqually earthquake evaluated approximately 60,000 chimneys through block-by-block coverage of about 50 km 2 , identifying a total of 1556 damaged chimneys. Chimney damage was strongly clustered in certain areas, in particular in the neighborhood of West Seattle where prior damage was also noted and evaluated after the 1965 earthquake. Our results showed that damage produced by the 2001 earthquake did not obviously correspond to distance from the earthquake epicenter, soft soils, topography, or slope orientation. Chimney damage correlates well to instrumented strong-motion measurements and compiled resident-reported ground-shaking intensities, but it offers much finer spatial resolution than these other data sources. In general, most areas of greatest chimney damage coincide with best estimated locations of strands of the Seattle fault zone. The edge of that zone also coincides with areas where chimney damage dropped abruptly over only one or two blocks' distance. The association between shaking intensity and fault-zone structure suggests that abrupt changes in the depth to bedrock, edge effects at the margin of the Seattle basin, or localized trapping of seismic waves in the Seattle fault zone may be significant contributory factors in the distribution of chimney damage.

Quantification of focusing effects of the semi-spherical and semi-cylindrical synclinal basement topography on ground motion characteristics

“…The basement focusing effects caused an anomalous damage to only unreinforced brick chimneys in western Seattle, Washington during the 2001 Nisqually earthquake (Booth et al 2004;Stephenson et al 2006) and very peculiar damage pattern in the Santa Monica area, Los Angeles basin during the Northridge earthquake of 1994 (Gao et al 1996;Hartzell et al 1997;Alex and Olsen 1998;Davis et al 2000). Davis et al (2000) inferred that the damage in the Santa Monica area occurred due to the focusing caused by the presence of several underground acoustic lenses at depths of around 3.0 km in the Los Angeles basin.…”

“…Baher and Davis (2003) performed a tomography experiment to find the subsurface velocity structure in the Santa Monica area and concluded that the anomalous damage was caused by the combined effects of the local site and the basement focusing. Based on the detailed damage survey of the Nisqually earthquake, Booth et al (2004) reported that the observed severe damage to collapses of chimneys only in the western Seattle do not correlate with the local geology and the chimney constructions. Stephenson et al (2006) and Frankel et al (2009) inferred that basement focusing of the direct waves played a major role in the damage of chimneys in western Seattle during Nisqually earthquake based on the analysis of 2D and 3D numerical simulations, respectively.…”

Study of role of basin shape in the site–city interaction effects on the ground motion characteristics

“…generated surface waves (Bard and Bouchon 1980;Kawase 1996;Graves et al 1998;Narayan 2005;Chaljub et al 2010;Semblat et al 2010;Paolucci and Morstabilini 2006), basement focusing effects (Gao et al 1996;Booth et al 2004;Kumar 2012, 2014a) and basin-transduced surface waves (Kawase 1993;Narayan 2010Narayan , 2012Narayan and Kumar 2014b). The effects of kinematic soil-structure interaction have been analysed for a long time, which cause diffraction of the incident body waves and largely affect the seismic response of the building, particularly massive or tall buildings situated on a soft soil (Housner 1954;Wong and Trifunac 1975).…”

Quantification of effects of geometry of sediment bedrock interface on ground motion in 3D basin with circular free surface

“…The basin-generated surface (BGS) waves caused unexpected intense damage in a zone with some width and parallel to basin-edge during Northridge earthquake of 1994 and Kobe earthquake of 1995 (Kawase, 1996;Graves et al, 1998;Pitarka et al, 1998). The subsurface synclinal basement focusing of the incident body waves caused intense anomalous damage to only unreinforced brick chimneys in West Seattle, Washington during the 2001 Nisqually earthquake and very peculiar damage pattern in the Santa Monica area, Los Angeles basin during the Northridge earthquake of 1994 (Gao et al, 1996;Davis et al, 2000;Booth et al, 2004;Narayan and Kumar, 2012;2014a). The focusing of body wave by the ridge-topography at the free surface causes complex ground motion amplification and de-amplification pattern along the ridge-flanks and a maximum amplification at the crest of the ridge (Geli et al, 1988;Narayan and Kumar, 2014b).…”