Seismic intensities, “size” of earthquakes and related parameters

1975 ◽  
Vol 65 (5) ◽  
pp. 1287-1313 ◽  
Author(s):  
Jack F. Evernden
Keyword(s):  
United States ◽  
High Risk ◽  
Simple Model ◽  
San Francisco ◽  
Regional Variation ◽  
Eastern United States ◽  
Owens Valley ◽  
Local Conditions ◽  
Return Times ◽  
Comparable Magnitude

Abstract The simple model of an earthquake used in Evernden, et al. (1973) was extended to the conterminous United States and observed patterns of isoseismals for major earthquakes studied in relation to the model. Regional attenuation, a known major factor controlling isoseismal patterns, was quantitatively evaluated. Incorporating this regional variation into the model results in the prediction that in terms of energy released, the San Francisco earthquake of 1906 was 50 times as large as Owens Valley 1872 and more than 100 times larger than the Charleston 1886 and New Madrid 1811 earthquakes. All of these were probably of comparable “magnitude”. Other relevant parameters are investigated. Analysis of probability of occurrence of major earthquakes in the Eastern United States suggests average annual return times of intensity X and IX of thousands of years at least. Presently unknown local conditions may lead to much greater probabilities at some localities, and the importance of developing procedures for determining regions of abnormally high risk is stressed.

The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

2019 ◽  
Vol 36 (1) ◽  
pp. 5-41 ◽  
Author(s):  
Mark D. Petersen ◽  
Allison M. Shumway ◽  
Peter M. Powers ◽  
Charles S. Mueller ◽  
Morgan P. Moschetti ◽  
...  
Keyword(s):  
United States ◽  
Los Angeles ◽  
Seismic Hazard ◽  
San Francisco ◽  
Urban Areas ◽  
Salt Lake ◽  
Sedimentary Basins ◽  
Hazard Model ◽  
Eastern United States ◽  
Ground Shaking

During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated epistemic uncertainties and aleatory variabilities, and new soil amplification factors; (3) in the western United States (WUS), amplified shaking estimates of long-period ground motions at sites overlying deep sedimentary basins in the Los Angeles, San Francisco, Seattle, and Salt Lake City areas were incorporated; and (4) in the conterminous United States, seismic hazard is calculated for 22 periods (from 0.01 to 10 s) and 8 uniform VS30 maps (ranging from 1500 to 150 m/s). We also include a description of updated computer codes and modeling details. Results show increased ground shaking in many (but not all) locations across the CEUS (up to ~30%), as well as near the four urban areas overlying deep sedimentary basins in the WUS (up to ~50%). Due to population growth and these increased hazard estimates, more people live or work in areas of high or moderate seismic hazard than ever before, leading to higher risk of undesirable consequences from forecasted future ground shaking.

Return Times of Large Earthquakes Cannot Be Estimated Correctly from Seismicity Rates: 1906 San Francisco and 1717 Alpine Fault Ruptures

2020 ◽  
Vol 91 (4) ◽  
pp. 2163-2169
Author(s):  
Max Wyss
Keyword(s):  
United States ◽  
San Francisco ◽  
San Andreas Fault ◽  
Return Time ◽  
Local Seismicity ◽  
Return Times ◽  
Alpine Fault ◽  
San Andreas ◽  
Seismicity Rates ◽  
Large Earthquakes

Abstract The unproven assumption that the Gutenberg–Richter (GR) relationship can be extrapolated to estimate the return time, Tr (1/probability of occurrence), of major and large earthquakes has been shown to be incorrect along 196 faults, so far. Here, two more examples of great, well-known faults that do not produce enough earthquakes to fulfill the hypothesis are analyzed. The 300 km section of the San Andreas fault, California, United States, that ruptured in 1906 in the M 8 San Francisco earthquake, produced 200 earthquakes with M≥2 in the last 52 yr, when about 250,000 such events are expected according to the hypothesis. Along a 250 km section that broke in an M 7.9 earthquake in 1717 along the Alpine fault, New Zealand, the number of reported M≥3.6 earthquakes during the last 34 yr was 100, when about 6000 would be expected, based on the hypothesis. Extrapolating the GR relationships for these two fault segments, one estimates Tr of mainshocks of M 8 to be about 10,000 and 100,000 for the 1717 and 1906 ruptures, respectively. Regardless of choice of analysis parameters, this is by factors of 10–400 larger than estimates based on paleogeology, tectonics, and geodesy. In addition, second catalogs for each case yield estimates of probabilities for M 8 earthquakes along the 1717 and 1906 rupture segments that differ by factors of about 2 and 80 (between 5000 and 98,000 yr) from the first respective catalogs. It follows that the probability of large earthquakes cannot be estimated correctly based on local seismicity rates along major faults.

Large-scale Regional Variation in Diatom-water Chemistry Relationships: Rivers of the Eastern United States

Hydrobiologia ◽  
2006 ◽  
Vol 561 (1) ◽  
pp. 27-57 ◽  
Author(s):  
Donald F. Charles ◽  
Frank W. Acker ◽  
David D. Hart ◽  
Charles W. Reimer ◽  
Patrick B. Cotter
Keyword(s):  
United States ◽  
Water Chemistry ◽  
Regional Variation ◽  
Large Scale ◽  
Eastern United States

Regional Variation in Patient Participation and Treatment among Acoustic Neuroma Association Survey Respondents Across the United States

2020 ◽  
Author(s):  
John P. Marinelli ◽  
Samuel A. Spear ◽  
Debbie L. Hahs-Vaughn ◽  
Robert J. Macielak ◽  
Michael J. Link ◽  
...  
Keyword(s):  
United States ◽  
Acoustic Neuroma ◽  
Patient Participation ◽  
Regional Variation ◽  
The United States

Transportation and the Environment

2017 ◽  
Vol 94 (3) ◽  
pp. 37-61
Author(s):  
Douglas R. Littlefield
Keyword(s):  
Nineteenth Century ◽  
San Francisco ◽  
Sierra Nevada ◽  
Mississippi River ◽  
San Joaquin Valley ◽  
Eastern United States ◽  
Major Health ◽  
San Joaquin River ◽  
Natural Wetlands ◽  
Prevailing View

Some histories of California describe nineteenth-century efforts to reclaim the extensive swamplands and shallow lakes in the southern part of California's San Joaquin Valley – then the largest natural wetlands habitat west of the Mississippi River – as a herculean venture to tame a boggy wilderness and turn the region into an agricultural paradise. Yet an 1850s proposition for draining those marshes and lakes primarily was a scheme to improve the state's transportation. Swampland reclamation was a secondary goal. Transport around the time of statehood in 1850 was severely lacking in California. Only a handful of steamboats plied a few of the state's larger rivers, and compared to the eastern United States, roads and railroads were nearly non-existent. Few of these modes of transportation reached into the isolated San Joaquin Valley. As a result, in 1857 the California legislature granted an exclusive franchise to the Tulare Canal and Land Company (sometimes known as the Montgomery franchise, after two of the firm's founders). The company's purpose was to connect navigable canals from the southern San Joaquin Valley to the San Joaquin River, which entered from the Sierra Nevada about half way up the valley. That stream, in turn, joined with San Francisco Bay, and thus the canals would open the entire San Joaquin Valley to world-wide commerce. In exchange for building the canals, the Montgomery franchise could collect tolls for twenty years and sell half the drained swamplands (the other half was to be sold by the state). Land sales were contingent upon the Montgomery franchise reclaiming the marshes. Wetlands in the mid-nineteenth century were not viewed as they are today as fragile wildlife habitats but instead as impediments to advancing American ideals and homesteads across the continent. Moreover, marshy areas were seen as major health menaces, with the prevailing view being that swampy regions’ air carried infectious diseases.

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