Characteristics of Free-Field Vertical Ground Motion during the Northridge Earthquake

1995 ◽  
Vol 11 (4) ◽  
pp. 515-525 ◽  
Author(s):  
Youself Bozorgnia ◽  
Mansour Niazi ◽  
Kenneth W. Campbell
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Free Field ◽  
Seismic Source ◽  
Spectral Ratio ◽  
Response Spectra ◽  
Northridge Earthquake ◽  
Attenuation Relationships ◽  
Vertical Ground Motion ◽  
Vertical Ground

Characteristics of response spectra of free-field vertical ground motion recorded during the 1994 Northridge earthquake are examined. Dependence of vertical and horizontal response spectra, and their ratio, on the site-to-source distance is investigated through development of attenuation relationships for vertical and horizontal spectral ordinates. The database includes 123 response spectra of the motions recorded at 41 alluvial sites. Vertical-to-horizontal (V/H) response spectral ratio is found to be strongly dependent on period and distance of site to the seismic source. V/H spectral ratio largely exceeds the commonly assumed value of 2/3, at short periods in the near-field region. The main characteristics of V/H spectral ratio for the Northridge earthquake are found to be qualitatively similar to those observed in the 1989 Loma Prieta, California, and in several other earthquakes recorded over the SMART-1 array in Taiwan. These characteristics are very likely to be universal.

Comparative Analysis of the Influence of Slope Terrain on Characteristics of Horizontal and Vertical Ground Motion Response Spectrum

2012 ◽  
Vol 446-449 ◽  
pp. 2279-2284
Author(s):  
Li Ping Wang ◽  
Yao Zhao
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Spectral Ratio ◽  
Earthquake Damage ◽  
Building Structures ◽  
Element Analysis ◽  
Motion Response ◽  
Vertical Ground Motion ◽  
Vertical Ground ◽  
Elastic Responses

All previous earthquake damage show earthquake damage of the buildings on the slope is serious than the buildings on flat ground, so it is important to analyze of the influence of slope terrain on characteristics of horizontal and vertical ground motion response spectrum. The horizontal and vertical seismic elastic responses of 28 viscoelastic rocky slopes by white noises excited, with height of 10m to70m and slope of 15°to 60°, are calculated by numerical finite element analysis method. The influence laws of height and degree of slope on horizontal and vertical ground motion response spectrum and response spectral ratio are analyzed. The distribution laws of the corresponding period of the maximum of response spectral ratios are contrasted. The maximum of amplification factor of design horizontal and vertical ground motion for structures on rock slopes are given to be the references to code for seismic design of building structures.

scholarly journals Near-Source Simulation of Strong Ground Motion in Amatrice Downtown Including Site Effects

Geosciences ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 186
Author(s):  
Alessandro Todrani ◽  
Giovanna Cultrera
Keyword(s):  
Ground Motion ◽  
Site Effects ◽  
Central Italy ◽  
Strong Motion ◽  
Seismic Source ◽  
Spectral Ratio ◽  
Intensity Measures ◽  
Standard Spectral Ratio ◽  
Heavy Damage ◽  
Strong Ground

On 24 August 2016, a Mw 6.0 earthquake started a damaging seismic sequence in central Italy. The historical center of Amatrice village reached the XI degree (MCS scale) but the high vulnerability alone could not explain the heavy damage. Unfortunately, at the time of the earthquake only AMT station, 200 m away from the downtown, recorded the mainshock, whereas tens of temporary stations were installed afterwards. We propose a method to simulate the ground motion affecting Amatrice, using the FFT amplitude recorded at AMT, which has been modified by the standard spectral ratio (SSR) computed at 14 seismic stations in downtown. We tested the procedure by comparing simulations and recordings of two later mainshocks (Mw 5.9 and Mw 6.5), underlining advantages and limits of the technique. The strong motion variability of simulations was related to the proximity of the seismic source, accounted for by the ground motion at AMT, and to the peculiar site effects, described by the transfer function at the sites. The largest amplification characterized the stations close to the NE hill edge and produced simulated values of intensity measures clearly above one standard deviation of the GMM expected for Italy, up to 1.6 g for PGA.

Near-Field Ground Motion of the 2002 Denali Fault, Alaska, Earthquake Recorded at Pump Station 10

2004 ◽  
Vol 20 (3) ◽  
pp. 597-615 ◽  
Author(s):  
W. L. Ellsworth ◽  
M. Celebi ◽  
J. R. Evans ◽  
E. G. Jensen ◽  
R. Kayen ◽  
...  
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Free Field ◽  
Monitoring And Control ◽  
Peak Acceleration ◽  
Permanent Displacement ◽  
Soil Response ◽  
Denali Fault ◽  
Field Recording ◽  
Pump Station

A free-field recording of the Denali fault earthquake was obtained by the Alyeska Pipeline Service Company 3 km from the surface rupture of the Denali fault. The instrument, part of the monitoring and control system for the trans-Alaska pipeline, was located at Pump Station 10, approximately 85 km east of the epicenter. After correction for the measured instrument response, we recover a seismogram that includes a permanent displacement of 3.0 m. The recorded ground motion has relatively low peak acceleration (0.36 g) and very high peak velocity (180 cm/s). Nonlinear soil response may have reduced the peak acceleration to this 0.36 g value. Accelerations in excess of 0.1 g lasted for 10 s, with the most intense motion occurring during a 1.5-s interval when the rupture passed the site. The low acceleration and high velocity observed near the fault in this earthquake agree with observations from other recent large-magnitude earthquakes.

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