Effects of anomalously weak and strong amplification of seismic waves in soil layers, with the example of two stations of KiK-net strong motion network of Japan

The ability of a strong-motion network to resolve wavefields can be described on three axes: frequency, amplitude, and space. While the need for spatial resolution is apparent, for practical reasons that axis is often neglected. TREMOR is a MEMS-based accelerograph using wireless Internet to minimize lifecycle cost. TREMOR instruments can economically augment traditional ones, residing between them to improve spatial resolution. The TREMOR instrument described here has dynamic range of 96 dB between ±2 g, or 102 dB between ±4 g. It is linear to <1% of full scale (FS), with a response function effectively shaped electronically. We developed an economical, very low noise, accurate (<1%FS) temperature compensation method. Displacement is easily recovered to 10-cm accuracy at full bandwidth, and better with care. We deployed prototype instruments in Oakland, California, beginning in 1998, with 13 now at mean spacing of ∼3 km—one of the most densely instrumented urban centers in the United States. This array is among the quickest in returning (PGA, PGV, Sa) vectors to ShakeMap, ∼75 to 100 s. Some 13 events have been recorded. A ShakeMap and an example of spatial variability are shown. Extensive tests of the prototypes for a commercial instrument are described here and in a companion paper.

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i1-net: The Iran Strong Motion Network

Seismological Research Letters ◽

10.1785/0220200417 ◽

2021 ◽

Author(s):

Mohammad Pourmohammad Shahvar ◽

Esmaeil Farzanegan ◽

Attiyeh Eshaghi ◽

Hossein Mirzaei

Keyword(s):

Earthquake Engineering ◽

Strong Motion ◽

Current Status ◽

Primary Input ◽

The Road ◽

Leading Position ◽

Hazard And Risk ◽

Ground Motion Records ◽

Strong Motion Network ◽

Strong Ground

Abstract Strong ground-motion records are the primary input data in earthquake engineering studies to improve understanding of seismic hazard and risk. As the overseer of the Iran Strong Motion Network (i1-net), the Road, Housing, and Urban Development Research Center occupies the leading position in this field in the country. With more than 1260 active accelerometers and a collection of over 14,129 earthquake recordings since 1973, the Iran Strong Motion Network is the major Iranian source of information for engineering seismology and earthquake engineering. The present article describes the current status and developments of the i1-net in the last 46 yr.

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RAIS: a real time strong-motion network in northern Italy

Annals of Geophysics ◽

10.4401/ag-4855 ◽

2011 ◽

Vol 54 (1) ◽

Author(s):

Paolo Augliera ◽

Marco Massa ◽

Ezio D'Alema ◽

Simone Marzorati

Keyword(s):

Real Time ◽

Strong Motion ◽

Northern Italy ◽

Strong Motion Network

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Coupled torsional dynamic analysis of a multistory building

Bulletin of the Seismological Society of America ◽

10.1785/bssa0630031025 ◽

1973 ◽

Vol 63 (3) ◽

pp. 1025-1039

Author(s):

Bruce M. Douglas ◽

Thomas E. Trabert

Keyword(s):

Ground Motion ◽

Degrees Of Freedom ◽

Seismic Waves ◽

Structural Response ◽

Tall Buildings ◽

Strong Motion ◽

Ambient Vibration ◽

Simultaneous Application ◽

Vibration Data ◽

Horizontal Ground Motion

abstract The coupled bending and torsional vibrations of a relatively symmetric 22-story reinforced concrete building in Reno, Nevada are studied. Analytical results are compared with observations obtained during the nuclear explosion FAULTLESS and to ambient vibration data. The fundamental periods of vibration observed during FAULTLESS were (TNS = 1.42, TEW = 1.81, TTORSION = 1.12 sec), and the calculated periods were (TNS = 2.14, TEW = 2.07, TTORSION = 1.90 sec). It was estimated that between 25 and 45 per cent of the total available nonstructural stiffness was required to explain the differences in the observed and calculated fundamental periods. Each floor diaphragm in the system was allowed three degrees of freedom-two translations and a rotation. It was found that coupled torsional motions can influence the response of structural elements near the periphery of the structure. Strong-motion structural response calculations comparing the simultaneous use of both components of horizontal ground motion to a single component analysis showed that the simultaneous application of both components of ground motion can significantly alter the response of lateral load-carrying elements. Differences of the order of 45 per cent were observed in the frames near the ends of the structure. Also, it was shown that the overall response of tall buildings is sensitive not only to the choice of input ground motion but also to the orientation of the structure with respect to the seismic waves.

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Horizontal particle velocity and its relation to magnitude in the Western United States

Bulletin of the Seismological Society of America ◽

10.1785/bssa0690062037 ◽

1979 ◽

Vol 69 (6) ◽

pp. 2037-2061

Author(s):

A. F. Espinosa

Keyword(s):

United States ◽

Data Base ◽

San Francisco ◽

Seismic Waves ◽

Scaling Law ◽

Direct Determination ◽

Strong Motion ◽

Western United States ◽

Short Period ◽

Horizontal Particle

abstract A magnitude (ML) scaling law has been derived from the strong-motion data base of the San Fernando earthquake of February 9, 1971, and the results have been compared with other strong-motion recordings obtained from 62 earthquakes in the Western United States. The relationship derived is ML = 3.21 + 1.35 log10Δ + log10v. An excellent agreement was obtained between the determined ML values in this study and those evaluated by Kanamori and Jennings (1978). This scaling law is applicable to the collected data from 63 earthquakes whose local magnitudes range from about 4.0 to 7.2, recorded at epicentral distances between about 5 to 300 km, and with short-period seismic waves in the range of 0.2 to 3.0 sec. The Long Beach earthquake of 1933, with an ML = 6.3 (PAS) and an ML = 6.43 ± 0.36 as determined by Kanamori and Jennings is in agreement with an ML = 6.49 ± 0.32 obtained in this study. The Imperial Valley earthquake of 1940, with an ML = 6.5 (PAS), compares well with an ML = 6.5 as determined in this study. The Kern County earthquake of 1952, with an ML = 7.2 (BRK), is in fairly good agreement with the ML = 7.0 ± 0.2 obtained in this investigation. This value is significantly lower than the commonly quoted 7.7 value for this event. The San Francisco earthquake of 1957, with an ML = 5.3 (BRK), agrees very well with an ML = 5.3 ± 0.1 as determined in this study. The Parkfield earthquake of 1966 has an ML = 5.8 ± 0.3, which is consistent with the 5.6 (PAS). The procedure developed here is applied to the data base obtained from the Western United States strong-motion recordings. The procedure allows the evaluation of ML for moderate and larger earthquakes from the first integration of the strong-motion accelerograms and allows the direct determination of ML from the scaled amplitudes in a rapid, economical, and accurate manner. It also has allowed for the extension of the trend of the attenuation curve for horizontal particle velocities at distances less than 5 km for different size events.

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