Strong-motion seismograph station listing

Epicentral intensities and damage in the Hebgen Lake, Montana, earthquake of August 17, 1959

Bulletin of the Seismological Society of America ◽

10.1785/bssa0520020181 ◽

1962 ◽

Vol 52 (2) ◽

pp. 181-234

Author(s):

Karl V. Steinbrugge ◽

William K. Cloud

Keyword(s):

Ground Motions ◽

Strong Motion ◽

Fault Scarp ◽

Rock Falls ◽

Small Unit ◽

The Earth ◽

Major Fault ◽

Seismograph Station ◽

Fault Scarps ◽

Earth Fill

ABSTRACT An extensive fault scarp system was formed during the Hebgen Lake earthquake of August 17, 1959 (11:37:15 p.m., M.S.T., Gutenberg-Richter magnitude 7.1). Bedrock beneath Hebgen Lake warped, rotated, and caused a seiche in the lake. A major landslide dammed Madison Canyon, causing a lake to form above the slide. An estimated 19 persons were buried by the slide. Other slides and rock falls took out sections of the main highway north of Hebgen Lake and closed many roads in Yellowstone Park. Small unit masonry structures as well as wooden buildings along the major fault scarps usually survived with little damage when subjected only to vibratory forces. The unit masonry buildings, in particular, had little or no earthquake bracing. Intensity at the major scarp has been given a Modified Mercalli Scale rating of X. However, the maximum intensity ratings based on vibratory motion even a few feet away from the scarps were VII or VIII. Within the limits of observation there was little or no reduction in vibratory intensity 5 to 10 miles away compared to that at the fault. This is not to say that the ground motions were similar. At the closest strong-motion seismograph station (Bozeman, 58 miles from the epicenter) maximum recorded acceleration was about 7 per cent gravity. The earthquake was generally felt in about a 600,000 square mile area, mostly north of the instrumental epicenter. The earth-fill Hebgen Dam was within 1000 feet of a major scarp. The dam was significantly damaged, but it continued to be an effective structure.

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The 1997 Umbria-Marche (central Italy) earthquake sequence: Insights on the mainshock ruptures from near source strong motion records

Geophysical Research Letters ◽

10.1029/1998gl005285 ◽

1999 ◽

Vol 26 (20) ◽

pp. 3165-3168 ◽

Cited By ~ 24

Author(s):

Aldo Zollo

Keyword(s):

Central Italy ◽

Strong Motion ◽

Earthquake Sequence ◽

Strong Motion Records ◽

Central Italy Earthquake

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THE EMPIRICAL GREEN’S FUNCTION TECHNIQUE MODIFICATION FOR ACCELEROGRAM SYNTHESIS IN LOWSEISMICITY REGIONS

Engineering survey ◽

10.25296/1997-8650-2018-12-5-6-72-80 ◽

2018 ◽

Vol 12 (5-6) ◽

pp. 72-80

Author(s):

A. A. Krylov

Keyword(s):

Green’S Function ◽

Green's Function ◽

Main Shock ◽

Amplitude Spectrum ◽

Strong Motion ◽

Function Technique ◽

Focal Region ◽

Empirical Green’S Function ◽

Epicentral Zone ◽

Empirical Green's Function

In the absence of strong motion records at the future construction sites, different theoretical and semi-empirical approaches are used to estimate the initial seismic vibrations of the soil. If there are records of weak earthquakes on the site and the parameters of the fault that generates the calculated earthquake are known, then the empirical Green’s function can be used. Initially, the empirical Green’s function method in the formulation of Irikura was applied for main shock record modelling using its aftershocks under the following conditions: the magnitude of the weak event is only 1–2 units smaller than the magnitude of the main shock; the focus of the weak event is localized in the focal region of a strong event, hearth, and it should be the same for both events. However, short-termed local instrumental seismological investigation, especially on seafloor, results usually with weak microearthquakes recordings. The magnitude of the observed micro-earthquakes is much lower than of the modeling event (more than 2). To test whether the method of the empirical Green’s function can be applied under these conditions, the accelerograms of the main shock of the earthquake in L'Aquila (6.04.09) with a magnitude Mw = 6.3 were modelled. The microearthquake with ML = 3,3 (21.05.2011) and unknown origin mechanism located in mainshock’s epicentral zone was used as the empirical Green’s function. It was concluded that the empirical Green’s function is to be preprocessed. The complex Fourier spectrum smoothing by moving average was suggested. After the smoothing the inverses Fourier transform results with new Green’s function. Thus, not only the amplitude spectrum is smoothed out, but also the phase spectrum. After such preliminary processing, the spectra of the calculated accelerograms and recorded correspond to each other much better. The modelling demonstrate good results within frequency range 0,1–10 Hz, considered usually for engineering seismological studies.

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