Duration of strong ground motion in terms of earthquake magnitude, epicentral distance, site conditions and site geometry

1994 ◽  
Vol 23 (9) ◽  
pp. 1023-1043 ◽  
Author(s):  
E. I. Novikova ◽  
M. D. Trifunac
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Epicentral Distance ◽  
Earthquake Magnitude ◽  
Site Conditions ◽  
Strong Ground

30 Ooctober 2020 Samos-Sigacik Earthquake: On Strong Ground Motion and Local Site Amplification

2021 ◽  
Author(s):  
Eser Çakti ◽  
Karin Sesetyan ◽  
Ufuk Hancilar ◽  
Merve Caglar ◽  
Emrullah Dar ◽  
...  
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Strong Ground Motion ◽  
Epicentral Distance ◽  
Strong Motion ◽  
Aegean Sea ◽  
Site Amplification ◽  
Local Site ◽  
Basin Effects ◽  
Strong Ground

<p>The Mw 6.9 earthquake that took place offshore between the Greek island of Samos and Turkey’s İzmir province on 30 October 2020 came hardly as a surprise. Due to the extensional tectonic regime of the Aegean and high deformation rates, earthquakes of similar size frequently occur in the Aegean Sea on fault segments close to the shores of Turkey, affecting the settlements on mainland Turkey and on the Greek Islands. Samos-Sigacik earthquake had a normal faulting mechanism. It was recorded by the strong motion networks in Turkey and Greece. Although expected, the earthquake was an  outstanding event in the sense of  highly localized, significant levels of building damage as a result of amplified ground motion levels. This presentation is an overview of strong ground motion characteristics of this important event both regionally and locally. Mainshock records suggest that local site effects, enhanced by basin effects could be responsible for structural damage in central Izmir, the third largest city of Turkey located at 60-70 km epicentral distance. We installed a seven-station network in Bayraklı and Karşıyaka districts of İzmir within three days of the mainshock in search of site and basin effects.  Through analysis of recorded aftershocks we explore the amplification characeristics of soils in the two aforementioned districts  and try to understand the role basin effects might have played in the resulting ground motion levels and consequently damage. </p>

An intensity survey of households affected by the Northridge, California, earthquake of 17 January 1994

1998 ◽  
Vol 88 (2) ◽  
pp. 441-462
Author(s):  
L. A. Dengler ◽  
J. W. Dewey
Keyword(s):  
Survey Data ◽  
Ground Motion ◽  
Strong Ground Motion ◽  
Telephone Survey ◽  
Epicentral Distance ◽  
Postal Questionnaire ◽  
Phone Survey ◽  
Subjective Judgments ◽  
Earthquake Education ◽  
Strong Ground

Abstract Following the Northridge, California, earthquake of 17 January 1994, the Humboldt Earthquake Education Center (HEEC) conducted a telephone survey of approximately 6000 adults from within the felt region to study the earthquake's effects on individual households. We tabulate human responses to the earthquake and observations of the earthquake's effects on inanimate objects from the HEEC survey as a function of independently assigned U.S. Geological Survey Modified Mercalli (USGS MM) intensity for the same communities. Human responses and subjective judgments about the severity of shaking, when averaged over a large number of samples, are useful discriminants of the levels of strong ground motion up to those associated with USGS MM intensity VII, notwithstanding that individual human responses and subjective judgments are notoriously unreliable. A threshold of strong ground motion corresponds to USGS MM intensity of about VII, above which over 40% of respondents described the earthquake as “violent” and most people reported difficulty standing, furniture displaced, and some damage to their homes. Even at intensities VIII and IX, however, relatively few people (about 15%) described their reaction as “panic” and only about 12% reported major damage to their homes. The HEEC phone-survey data show that, in communities of low to moderate shaking, USGS MM intensities estimated from a single postal questionnaire are quite robust. At USGS MM intensity of V and below, 88% of USGS MM intensities determined from postal questionnaires are within one intensity unit of intensities determined from the more numerous HEEC telephone survey data for the same community. We introduce the concept of a community decimal intensity scale (CDI) based on telephone-survey data and calibrated to agree on average with the USGS MM intensities. The CDIs are more regularly distributed than the USGS MM intensities and show much less scatter when plotted as a function of epicentral distance. CDIs show promise as a tool for comparing regional attenuation, for delineating variations in shaking strength within areas mapped as a single MM zone, and for rapid preliminary intensity estimates utilizing electronic media.

Some Aspects of the Seismic Scaling and the Strong Ground Motion of the Eastern Missouri Earthquake of January 12, 1984

1987 ◽  
Vol 58 (2) ◽  
pp. 53-58 ◽  
Author(s):  
Otto W. Nuttli ◽  
David S. Bowling ◽  
J. E. Lawson ◽  
Randall Wheeler
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Epicentral Distance ◽  
Vertical Component ◽  
Strong Motion ◽  
Radial Component ◽  
Transverse Component ◽  
Corner Frequency ◽  
Scaling Relation ◽  
Strong Ground

Abstract Strong-motion records from a velocity meter were recorded at an epicentral distance of 4.5 km from the January 12, 1984 eastern Missouri earthquake of mb = 3.0. Peak values of ground velocity, associated with only one or two wave cycles, are: transverse component, 0.18 cm/sec; radial component, 0.16 cm/sec; vertical component, 0.12 cm/sec. The levels of the sustained motion, which extends from the onset of S to about 0.4 sec later, are: transverse component, 0.064 cm/sec; radial component, 0.061 cm/sec; vertical component, 0.061 cm/sec. The data are consistent with a spectral scaling relation assuming either a 3.5 or 4.0 slope of the logarithm of the seismic moment versus the logarithm of the corner frequency, but cannot be used to choose between the two relations.

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