Sliding and overturning potential of Christchurch 2011 earthquake records

Abstract

SUMMARY The 22 February 2011 Mw 6.3 earthquake produced a number of unique accelerograms in the city of Christchurch and the port of Lyttelton. Four of these records are analyzed in this paper. The two are from the Christchurch Catholic Cathedral College and Christchurch Hospital stations in the center of the city, which were placed on top of loose sandy soils that suffered softening due to liquefaction; one is from the Lyttelton station, Lyttelton Port Company, on a rock outcrop; and one is from the station at the Heathcote Valley Primary School, on stiff colluvial silts and sands near the edge of a steep and stiff sedimentary basin. The (elastic) response spectra are discussed and related to some salient characteristics of the motions. Symmetric and asymmetric sliding of a block resting through Coulomb friction on horizontal or inclined planes and rocking–overturning of rigid blocks, when excited at their base by these records, offer a strong indication of their ‘destructiveness potential’. The corresponding sliding and overturning spectra of the 2011 records are compared with those of some historic accelerograms to get an understanding of the severity of ground shaking that caused 170 deaths and heavy geotechnical and structural damage in the city of Christchurch. The possible role played by the unusually large vertical accelerations is also explored. Copyright © 2012 John Wiley & Sons, Ltd.

Building contents sliding demands in elastically responding structures

“…(iii) With a focus on sliding-related failure, no consideration is given on damage caused by rocking of contents. (iv) Previous studies showed both positive and negative influence on sliding demand when considering vertical acceleration [5,13,17,20,27,30,31]. To simplify the problem, the effect of vertical accelerations on frictional bond strength is not considered in this study.…”

“…Taniguchi [27] confirmed the above trends in sliding displacements due to vertical accelerations. Gazetas and his co-workers, however, stated a negligible influence due to vertical motions [30,31]. The above difference may be a result of the different friction coefficients and context of the horizontal and vertical ground shakings considered in the investigations (e.g.…”

“…The above difference may be a result of the different friction coefficients and context of the horizontal and vertical ground shakings considered in the investigations (e.g. in Gazetas et al's investigation, the focus was on near-fault motions [30] and friction coefficient was limited to 0.2 for contents sliding on a horizontal plane and subjected to horizontal and vertical motions simultaneously [31]). In based-isolated buildings, numerical studies [20] have shown negligible influence of vertical motion, and even experimental results [5] suggest that vertical motion is not detrimental when the peak vertical acceleration remains below 2 g.…”

“…These include investigations into block sliding response to earthquake motions [13][14][15][16][17][18][19][20][21][22][23][24], derivation of formulations and criteria for rigid bodies sliding due to base excitation [21,[25][26][27], and in-field analyses of sliding rock blocks [28][29][30][31][32]. Also, many observations of contents sliding and falling off shelves have been obtained from the 1976 San Fernando, the 1989 Loma Prieta, the 1994 Northridge, and the recent Canterbury earthquakes [33][34][35][36].…”

Phase errors in accelerometer arrays: An analysis based on collocated sensors and FEM

“…Still, analysis of recordings from certain accelerometer arrays has permitted to identify peak ground accelerations of exceptional magnitude and strong contrasts in the distribution of earthquake motions [15], as well as to understand effects such as the progressive response of bridges to moving loads [9].…”