Using safety inspection data to estimate shaking intensity for the 1994 Northridge earthquake

1998 ◽  
Vol 88 (5) ◽  
pp. 1243-1253
Author(s):  
Katharina Thywissen ◽  
John Boatwright
Keyword(s):  
Los Angeles ◽  
Census Tract ◽  
Residential Buildings ◽  
Intensity Level ◽  
Northridge Earthquake ◽  
Single Family ◽  
Census Tracts ◽  
Wood Frame ◽  
Inspection Data ◽  
1994 Northridge Earthquake

Abstract We map the shaking intensity suffered in Los Angeles County during the 17 January 1994, Northridge earthquake using municipal safety inspection data. The intensity is estimated from the number of buildings given red, yellow, or green tags, aggregated by census tract. Census tracts contain from 200 to 4000 residential buildings and have an average area of 6 km2 but are as small as 2 and 1 km2 in the most densely populated areas of the San Fernando Valley and downtown Los Angeles, respectively. In comparison, the zip code areas on which standard MMI intensity estimates are based are six times larger, on average, than the census tracts. We group the buildings by age (before and after 1940 and 1976), by number of housing units (one, two to four, and five or more), and by construction type, and we normalize the tags by the total number of similar buildings in each census tract. We analyze the seven most abundant building categories. The fragilities (the fraction of buildings in each category tagged within each intensity level) for these seven building categories are adjusted so that the intensity estimates agree. We calibrate the shaking intensity to correspond with the modified Mercalli intensities (MMI) estimated and compiled by Dewey et al. (1995); the shapes of the resulting isoseismals are similar, although we underestimate the extent of the MMI = 6 and 7 areas. The fragility varies significantly between different building categories (by factors of 10 to 20) and building ages (by factors of 2 to 6). The post-1940 wood-frame multi-family (≧5 units) dwellings make up the most fragile building category, and the post-1940 woodframe single-family dwellings make up the most resistant building category.

A composite source model of the 1994 Northridge earthquake using genetic algorithms

1996 ◽  
Vol 86 (1B) ◽  
pp. S71-S83 ◽  
Author(s):  
Yuehua Zeng ◽  
John G. Anderson
Keyword(s):  
Genetic Algorithms ◽  
Los Angeles ◽  
Strong Motion ◽  
Computation Time ◽  
Source Model ◽  
Northridge Earthquake ◽  
Good Convergence ◽  
Strong Ground Motion Prediction ◽  
Composite Source Model ◽  
1994 Northridge Earthquake

Abstract The 17 January 1994 Northridge earthquake (Mw 6.7) occurred on a buried thrust fault in the northwest Los Angeles metropolitan area. We investigate the source process of this earthquake using the CSMIP strong motion records and a composite source model developed by Zeng et al. (1994a) for realistic earthquake strong ground motion prediction. Our previous studies demonstrated the realism of the synthetic strong motions generated from the composite source model by comparing them with observed records from earthquakes in many areas of the world. This article addresses an inverse study of the problem to find a specific composite source model for the Northridge earthquake. This is done by adjusting the location of a suite of composite subevents, using genetic algorithms (Holland, 1975), to best match the observed waveforms. A test run of the genetic algorithm on synthetic data sets finds a very good convergence of the approach. We reduce largely the intensive computation time by identifying subevents with major contribution to the waveform fit. Our result for the 1994 Northridge earthquake indicates a complex earthquake rupture process with three large slip zones: one at the hypocenter and the other two to the west of the hypocenter. We then use this model to compute the high-frequency strong-motion velocity and acceleration. The results show that the composite source model provides a very realistic broadband source description for the Northridge earthquake.

scholarly journals Tightness of Single-Family Buildings Made in Prefabricated Wood Frame Technology

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4500
Author(s):  
Artur Nowoświat ◽  
Iwona Pokorska-Silva ◽  
Mateusz Konewecki
Keyword(s):  
Residential Buildings ◽  
Statistical Hypothesis ◽  
Single Family ◽  
Qualitative And Quantitative ◽  
Roof Structure ◽  
Wood Frame ◽  
Frame Technology ◽  
The Impact ◽  
Wall System ◽  
Made In

The overall objective of the study is to determine the influence of various factors on the tightness of frame-based buildings. The study presents airtightness tests—Blow Doors Tests of single-family residential buildings made in the prefabricated wood frame technology. Primarily, the impact of selected quantitative and qualitative parameters on the determined quantity n50 was defined. For that purpose, correlation analyses were performed and the statistical hypothesis stating that there is no statistically significant linear relationship between n50 (a multiplication factor of air exchange in the building effected by pressure difference of 50 Pa) and the specified qualitative and quantitative parameters was verified. The hypothesis was verified using the F and χ2 statistics. The studies demonstrated that there are no grounds to reject the research hypothesis. The obtained results formulate a comprehensive conclusion that allows to test the tightness of buildings made in the prefabricated wood frame technology and makes the tightness results independent of many features of the examined building. Ultimately, the tightness results are only dependent on the leak of the examined object. They do not depend on roof structure, wall system, floor area, cubature, number of window openings, porch.

scholarly journals The city of Los Angeles experience during the 1994 Northridge earthquake

1997 ◽  
Vol 30 (1) ◽  
pp. 2-13
Author(s):  
N. Delli Quadri
Keyword(s):  
Los Angeles ◽  
Disaster Response ◽  
The Other ◽  
Northridge Earthquake ◽  
Emergency Situations ◽  
The World ◽  
Surrounding Areas ◽  
The City ◽  
1994 Northridge Earthquake

A successful disaster response depends greatly on how well and how quickly resources can be mobilized and allocated. To do this effectively, there must be a system in place that can collect, prepare and send the resources; and a system at the other end that can effectively receive and deploy them. The information gained from the Northridge Earthquake and the lesson learned by the City of Los Angeles and its surrounding areas can be of great value to jurisdictions around the world in planning and preparing for future disaster and emergency situations.

Homogeneity versus Heterogeneity in Household Structure: The Recent Experience of Twenty US Cities

1986 ◽  
Vol 18 (6) ◽  
pp. 715-727 ◽  
Author(s):  
P Gober
Keyword(s):  
Census Tract ◽  
Household Composition ◽  
Household Structure ◽  
Recent Experience ◽  
Single Family ◽  
Census Tracts ◽  
Census Tract Level ◽  
Family Housing ◽  
Us Cities

This paper is an investigation of the variation in household structure at the census tract level in twenty US cities between 1970 and 1980. Results indicate that households were, in 1980, more likely to reside in proximity to households with different compositions. In 1980 the most genuinely diverse census tracts, in terms of household composition, were in neighborhoods with recently constructed, single-family housing.

Estimation of Earthquake Losses to Buildings

1997 ◽  
Vol 13 (4) ◽  
pp. 703-720 ◽  
Author(s):  
Charles A. Kircher ◽  
Robert K. Reitherman ◽  
Robert V. Whitman ◽  
Christopher Arnold
Keyword(s):  
Los Angeles ◽  
Model Building ◽  
Economic Losses ◽  
Northridge Earthquake ◽  
Single Family ◽  
Ground Shaking ◽  
Ground Failure ◽  
New Methods ◽  
Earthquake Losses ◽  
Earthquake Loss

This paper describes methods for estimating building losses that were developed for the FEMA/NIBS earthquake loss estimation methodology (Whitman et al., 1997). These methods are of a new form and represent a significant step forward in the prediction of earthquake impacts. Unlike previous building loss models that are based on Modified Mercalli Intensity, the new methods use quantitative measures of ground shaking (and ground failure) and analyze model building types in a similar manner to the engineering analysis of a single structure. Direct economic losses predicted by these new methods for typical single-family homes compare well with observed losses to Los Angeles County residences damaged by the 1994 Northridge Earthquake.

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