Seismology

1995 ◽  
Vol 11 (2_suppl) ◽  
pp. 1-12
Keyword(s):  
Los Angeles ◽  
Seismic Hazard ◽  
Focal Depth ◽  
High Rate ◽  
Northridge Earthquake ◽  
Los Angeles Basin ◽  
San Fernando ◽  
Northern Edge ◽  
San Fernando Valley ◽  
The Moment

The Northridge earthquake occurred on January 17, 1994, at 4:31 a.m. Pacific Standard Time. The hypocenter was about 32 km west-northwest of Los Angeles in the San Fernando Valley at a relatively deep focal depth of 19 km. The moment magnitude for the earthquake is Mw6.7. The earthquake occurred on a south-southwest dipping thrust ramp beneath the San Fernando Valley and, thus, reemphasized the seismic hazard of concealed faults in the greater Los Angeles region. The Northridge earthquake also indicates a continuing high rate of seismicity along the northern edge of the Los Angeles basin.

Interpretation of significant ground-response and structure strong motions recorded during the 1994 Northridge earthquake

1996 ◽  
Vol 86 (1B) ◽  
pp. S231-S246 ◽  
Author(s):  
A. F. Shakal ◽  
M. J. Huang ◽  
R. B. Darragh
Keyword(s):  
Flexible Structures ◽  
Northridge Earthquake ◽  
Moment Frame ◽  
Ground Response ◽  
Short Period ◽  
Frame Buildings ◽  
Story Drift ◽  
San Fernando ◽  
San Fernando Valley ◽  
The Moment

Abstract Some of the largest accelerations and velocities ever recorded at ground-response and structural sites occurred during the Northridge earthquake. These motions are greater than most existing attenuation models would have predicted. Although the motions are large, the correspondence between measured acceleration and damage requires further study, since some sites with high acceleration experienced only moderate damage. Also, some peak vertical accelerations were larger than the horizontal, but in general, they are smaller and fit the pattern observed in previous earthquakes. Strong-motion records processed to date show significant differences in acceleration and velocity waveforms and amplitudes across the San Fernando Valley. Analysis of processed data from several buildings in the San Fernando Valley indicates that short-period buildings such as shear-wall buildings experienced large forces and relatively low inter-story drift during the Northridge earthquake. However, long-period (1 to 5 sec) steel or concrete moment-frame buildings experienced large inter-story drift. For this earthquake, accelerations did not always amplify from base to roof for flexible structures like the moment-frame buildings, but the displacements were always larger at the roof. The drifts at many of the moment-frame buildings were larger than the drift limit for working stress design in the building code. The records from a base-isolated building indicate that high-frequency motion was reduced significantly by the isolators. The isolators deformed about 3.5 cm, which is much less than the design displacement. The records from a parking structure show important features of the seismic response of this class of structure.

Fire-Related Aspects

1995 ◽  
Vol 11 (2_suppl) ◽  
pp. 419-435 ◽  
Keyword(s):  
Los Angeles ◽  
Fire Department ◽  
Northridge Earthquake ◽  
Mutual Aid ◽  
Fire Departments ◽  
Santa Monica ◽  
San Fernando ◽  
Wide Scale ◽  
San Fernando Valley ◽  
Alternative Water

The Northridge earthquake caused high shaking intensities for several million persons in the northern Los Angeles region, centered in the San Fernando Valley. Fire protection for the heavily damaged area is furnished primarily by Los Angeles City Fire Department and, to a lesser extent, Los Angeles County, Santa Monica, and other departments. The earthquake resulted in about 110 fires, about 80% of which were structure fires. Of these, most were in single-or multi-family dwellings. All of the initial fires were out before noon despite impaired communications, wide-scale failure of firefighting water supply in large parts of the San Fernando Valley, and other problems. Alternative water supplies, such as backyard swimming pools, were employed in some cases. Mutual aid was requested by fire departments in the affected area, but resources from outside the Los Angeles metropolitan area were not required.

An autoethnographic account of urban restructuring and neighborhood change in Los Angeles’ San Fernando Valley

2019 ◽  
Vol 27 (3) ◽  
pp. 379-394 ◽  
Author(s):  
Stefano Bloch
Keyword(s):  
Los Angeles ◽  
Cultural Landscape ◽  
Neighborhood Change ◽  
General Motors ◽  
Northridge Earthquake ◽  
Urban Restructuring ◽  
Time Period ◽  
San Fernando ◽  
San Fernando Valley ◽  
Children Welfare

Suburbs have long been glossed over by critical urbanists for being culturally, even if not spatially, less than urban. In Los Angeles, it is the San Fernando Valley that has received such treatment as scholars have tended toward the metropolitan basin. In this article, I aim to help re-center the San Fernando Valley as a complex and conflictual cultural landscape through an autoethnographic exploration of four moments of urban restructuring in the Panorama City neighborhood. I provide a personal account of how a succession of events – the 1992 LA Riot, 1993 General Motors Plant closure, 1994 Northridge earthquake, and 1996 dismantling of the Aid for Families with Dependent Children welfare program – led to the disruption and partial destruction of a neighborhood. I situate these moments of crisis within the context of a civil gang injunction and outbreak of abject violence during this time period, which further destabilized the neighborhood and informed my own decision to pick up a gun.

Application of Fracture Mechanics to Steel Connections in Moment Frames under Seismic Loading

1997 ◽  
Vol 1 (1) ◽  
pp. 23-37 ◽  
Author(s):  
C. Joh ◽  
W.F. Chen
Keyword(s):  
Fracture Mechanics ◽  
Steel Structures ◽  
Northridge Earthquake ◽  
Moment Frames ◽  
Moment Connections ◽  
Related Factors ◽  
Steel Connections ◽  
Moment Connection ◽  
San Fernando ◽  
The Moment

The 6.8 magnitude Northridge earthquake that shook California's San Fernando Valley on January 17 in 1994, did not cause the collapse of any steel structures but connections, confidently designed and constructed in the past with traditional code simplification and common site welding techniques, were discovered not to meet our expectations. This paper reviews connection failures during the 1994 Northridge earthquake and the design philosophy and examines the post-Northridge earthquake experimental and analytical researches. Possible causes of the moment connections damage are categorized into three classes; welding-related factors, design-related factors, and material-related factors. For the analyses, the idealizations of the moment connection considering each factor are studied. From the idealization of the moment connection, the five-plate model is analyzed to investigate the stress concentration and stress state of the connection. The equivalent design crack models are investigated using the fracture mechanics approach.

2019 Ridgecrest Earthquake Reveals Areas of Los Angeles That Amplify Shaking of High-Rises

2020 ◽  
Vol 91 (6) ◽  
pp. 3370-3380
Author(s):  
Monica D. Kohler ◽  
Filippos Filippitzis ◽  
Thomas Heaton ◽  
Robert W. Clayton ◽  
Richard Guy ◽  
...  
Keyword(s):  
Los Angeles ◽  
Strong Motion ◽  
Ground Level ◽  
Site Amplification ◽  
Seismic Network ◽  
Los Angeles Basin ◽  
High Rise ◽  
The North ◽  
South Central ◽  
San Fernando

Abstract The populace of Los Angeles, California, was startled by shaking from the M 7.1 earthquake that struck the city of Ridgecrest located 200 km to the north on 6 July 2019. Although the earthquake did not cause damage in Los Angeles, the experience in high-rise buildings was frightening in contrast to the shaking felt in short buildings. Observations from 560 ground-level accelerometers reveal large variations in shaking in the Los Angeles basin that occurred for more than 2 min. The observations come from the spatially dense Community Seismic Network (CSN), combined with the sparser Southern California Seismic Network and California Strong Motion Instrumentation Program networks. Site amplification factors for periods of 1, 3, 6, and 8 s are computed as the ratio of each station’s response spectral values combined for the two horizontal directions, relative to the average of three bedrock sites. Spatially coherent behavior in site amplification emerges for periods ≥3  s, and the maximum calculated site amplifications are the largest, by factors of 7, 10, and 8, respectively, for 3, 6, and 8 s periods. The dense CSN observations show that the long-period amplification is clearly, but only partially, correlated with the depth to basement. Sites with the largest amplifications for the long periods (≥3  s) are not close to the deepest portion of the basin. At 6 and 8 s periods, the maximum amplifications occur in the western part of the Los Angeles basin and in the south-central San Fernando Valley sedimentary basin. The observations suggest that the excitation of a hypothetical high-rise located in an area characterized by the largest site amplifications could be four times larger than in a downtown Los Angeles location.

Water Politics and the San Fernando Valley: The Role of Water Rights in the 1915 Annexation and 1996-2002 Secession Campaigns

2010 ◽  
Vol 92 (2) ◽  
pp. 93-116
Author(s):  
Jordan Scavo
Keyword(s):  
Los Angeles ◽  
Water Rights ◽  
Water Politics ◽  
Municipal Water ◽  
San Fernando ◽  
San Fernando Valley ◽  
The City

Municipal water rights played the central role in the 1913-1915 campaign to annex San Fernando Valley communities to the city of Los Angeles. Jordan Scavo explores why the water issue was downplayed by both sides in the 1996-2002 Valley secession campaign. He finds that the water rights debates are a measure of the extent to which the Valley and the city have become bound to each other.

scholarly journals Brief report on the January 17 1994 Northridge earthquake in Los Angeles

1994 ◽  
Vol 27 (1) ◽  
pp. 55-75
Author(s):  
Editor
Keyword(s):  
Surface Wave ◽  
Los Angeles ◽  
Press Release ◽  
Northridge Earthquake ◽  
Local Magnitude ◽  
Surface Wave Magnitude ◽  
Detailed Report ◽  
Information Centre ◽  
Standard Time ◽  
San Fernando

An earthquake struck the San Fernando Valley on January 17 at 4:30 am. Pacific Standard Time. The epicenter was located at 34°13' North, 118°3' West at a depth of 14.6km. The surface wave magnitude from the National Earthquake Information Centre was 6.6. The local magnitude was 6.4. Most of this information was prepared within a few days of the earthquake occurring and some of the material included in this report was issued as a press release. A more detailed report is currently being prepared by the Reconnaissance Team sent by the Society.

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