scholarly journals Near-source strong ground motions observed in the 22 February 2011 Christchurch earthquake

2011 ◽  
Vol 44 (4) ◽  
pp. 181-194 ◽  
Author(s):  
Brendon A. Bradley ◽  
Misko Cubrinovski
Keyword(s):  
Surface Waves ◽  
Site Response ◽  
Ground Motions ◽  
Response Spectra ◽  
Critical Examination ◽  
Acceleration Response ◽  
Strong Ground Motions ◽  
Nonlinear Site Response ◽  
Acceleration Response Spectra ◽  
Strong Ground

This manuscript provides a critical examination of the ground motions recorded in the near-source region resulting from the 22 February 2011 Christchurch earthquake. Particular attention is given to reconciling the observed spatial distribution of ground motions in terms of physical phenomena related to source, path and site effects. The large number of near-source observed strong ground motions show clear evidence of: forward-directivity, basin generated surface waves, liquefaction and other significant nonlinear site response. The pseudo-acceleration response spectra (SA) amplitudes and significant duration of strong motions agree well with empirical prediction models, except at long vibration periods where the influence of basin-generated surface waves and nonlinear site response are significant and not adequately accounted for in empirical SA models. Pseudo-acceleration response spectra are also compared with those observed in the 4 September 2010 Darfield earthquake and routine design response spectra used in order to emphasise the amplitude of ground shaking and elucidate the importance of local geotechnical characteristics on surface ground motions. The characteristics of the observed vertical component accelerations are shown to be strongly dependent on source-to-site distance and are comparable with those from the 4 September 2010 Darfield earthquake, implying the large amplitudes observed are simply a result of many observations at close distances rather than a peculiar source effect.

Bi-Directional Pseudo-Acceleration Response Spectra

2016 ◽  
Vol 10 (04) ◽  
pp. 1650007
Author(s):  
Anat Ruangrassamee ◽  
Chitti Palasri ◽  
Panitan Lukkunaprasit
Keyword(s):  
Seismic Design ◽  
Response Spectrum ◽  
Ground Motions ◽  
Strong Motion ◽  
Response Spectra ◽  
Acceleration Response ◽  
Acceleration Response Spectra ◽  
Acceleration Response Spectrum ◽  
Two Degree Of Freedom ◽  
Ratio Response

In seismic design, excitations are usually considered separately in two perpendicular directions of structures. In fact, the two components of ground motions occur simultaneously. This paper clarifies the effects of bi-directional excitations on structures and proposes the response spectra called “bi-directional pseudo-acceleration response spectra”. A simplified analytical model of a two-degree-of-freedom system was employed. The effect of directivity of ground motions was taken into account by applying strong motion records in all directions. The analytical results were presented in the form of the acceleration ratio response spectrum defined as the bi-directional pseudo-acceleration response spectrum normalized by a pseudo-acceleration response spectrum.

Strong ground motions recorded during earthquakes of May the 11th and 19th, 1962 in Mexico City

1964 ◽  
Vol 54 (1) ◽  
pp. 209-231
Author(s):  
Leonardo Zeevaert
Keyword(s):  
Mexico City ◽  
Ground Motions ◽  
Soft Clay ◽  
Response Spectra ◽  
The Other ◽  
Soil Conditions ◽  
Strong Ground Motions ◽  
Multistory Building ◽  
Local Soil ◽  
Strong Ground

abstract The ground accelerations during the earthquakes of May 11 and 19, 1962 were recorded in Mexico City on a soft clay bed that was formerly the floor of an old lake. Records were obtained from two accelerometers, one instrument was located in the basement of a multistory building and the other was located in a nearby park. Response spectra of the ground motions are presented and analysis is made of the local soil conditions with the view to explaining the characteristics of the spectrums.

A simple model for strong ground motions and response spectra

1988 ◽  
Vol 16 (2) ◽  
pp. 203-215 ◽  
Author(s):  
Erdal Safak ◽  
Charles Mueller ◽  
John Boatwright
Keyword(s):  
Simple Model ◽  
Ground Motions ◽  
Response Spectra ◽  
Strong Ground Motions ◽  
Strong Ground

scholarly journals Free Field Surface Motion at Different Site Types due to Near-Fault Ground Motions

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
Jagabandhu Dixit ◽  
D. M. Dewaikar ◽  
R. S. Jangid
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Free Field ◽  
Response Spectra ◽  
Response Analysis ◽  
Acceleration Response ◽  
Surface Motion ◽  
Near Fault ◽  
Acceleration Response Spectra ◽  
Site Category

Seismic hazards during many disastrous earthquakes are observed to be aggravating at the sites with the soft soil deposits due to amplification of ground motion. The characteristics of strong ground motion, the site category, depth of the soil column, type of rock strata, and the dynamic soil properties at a particular site significantly influence the free field motion during an earthquake. In this paper, free field surface motion is evaluated via seismic site response analysis that involves the propagation of earthquake ground motions from the bedrock through the overlying soil layers to the ground surface. These analyses are carried out for multiple near-fault seismic ground motions at 142 locations in Mumbai city categorized into different site classes. The free field surface motion is quantified in terms of amplification ratio, spectral relative velocity, and spectral acceleration. Seismic site coefficients at different time periods are also evaluated for each site category due to near-fault ground motions from the acceleration response spectra of free field surface motion at each site and the corresponding acceleration response spectra at a reference rock outcrop site.

Strong Motions on Land and Ocean Bottom: Comparison of Horizontal PGA, PGV, and 5% Damped Acceleration Response Spectra in Northeast Japan and the Japan Trench Area

2021 ◽  
Author(s):  
Yadab P. Dhakal ◽  
Takashi Kunugi ◽  
Wataru Suzuki ◽  
Takeshi Kimura ◽  
Nobuyuki Morikawa ◽  
...  
Keyword(s):  
Ground Motions ◽  
Response Spectra ◽  
Japan Trench ◽  
Ocean Bottom ◽  
Acceleration Response ◽  
Offshore Area ◽  
Acceleration Response Spectra ◽  
Short Period ◽  
Trench Area ◽  
Water Depths

ABSTRACT A large-scale permanent ocean-bottom seismograph network, named S-net, has been established in the Japan Trench area and consists of 150 observatories equipped with seismometers and tsunamimeters. Most stations at water depths <1500 m were buried to a depth of about 1 m while they were sited freely on the seafloors at greater water depths. To understand the characteristics of strong ground motions on the offshore area, we compared the horizontal vector peak ground accelerations (PGA), peak ground velocities (PGVs), and acceleration response spectra (ARS) between the land and S-net sites for nine earthquakes (5.3≤Mw≤7.1) using ground-motion prediction equations developed for Japan. We found that the observed values of PGAs and short-period (<0.5 s) ARS were generally similar between the land and S-net sites, whereas the PGVs and ARS for the periods longer than 0.5 s were apparently larger at the S-net sites. These results based on data covering a wide area on the seafloors were generally similar to the previous results based on limited ocean-bottom stations. However, analysis of the residuals, within the source-to-site distance of 200 km, revealed that the residual values were smaller in the shallow water region compared to those toward the Japan Trench, which is characterized by proximity to high Qs in the Pacific plate, the presence of thick unconsolidated sediments on the upper crust, and increasing heights of water columns. The difference of station settings in the shallow and deep water regions may also have contributed to the biased distribution of residuals at the short periods. Quantifications of these results are expected to contribute to the predictions of ground motions for earthquake early warning and seismic demand analysis of offshore facilities and await further analysis of a larger data set.

Sign in / Sign up

Export Citation Format

Share Document