Earthquake Faulting: Ground Motions and Deformations

This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.

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A subset of CyberShake ground-motion time series for response-history analysis

Earthquake Spectra ◽

10.1177/8755293020981970 ◽

2021 ◽

pp. 875529302098197

Author(s):

Jack W Baker ◽

Sanaz Rezaeian ◽

Christine A Goulet ◽

Nicolas Luco ◽

Ganyu Teng

Keyword(s):

Time Series ◽

Los Angeles ◽

Seismic Hazard ◽

Ground Motion ◽

Ground Motions ◽

Response Spectra ◽

Motion Time ◽

History Analysis ◽

Response History Analysis ◽

Simulated Ground Motions

This manuscript describes a subset of CyberShake numerically simulated ground motions that were selected and vetted for use in engineering response-history analyses. Ground motions were selected that have seismological properties and response spectra representative of conditions in the Los Angeles area, based on disaggregation of seismic hazard. Ground motions were selected from millions of available time series and were reviewed to confirm their suitability for response-history analysis. The processes used to select the time series, the characteristics of the resulting data, and the provided documentation are described in this article. The resulting data and documentation are available electronically.

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Ground-motion model for subduction earthquakes in northern South America

Earthquake Spectra ◽

10.1177/87552930211027585 ◽

2021 ◽

pp. 875529302110275

Author(s):

Carlos A Arteta ◽

Cesar A Pajaro ◽

Vicente Mercado ◽

Julián Montejo ◽

Mónica Arcila ◽

...

Keyword(s):

South America ◽

Ground Motion ◽

Ground Motions ◽

Strong Motion ◽

Motion Prediction ◽

Depth Range ◽

Ground Motion Prediction ◽

Natural Period ◽

Nazca Plate ◽

Northern South America

Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤ Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

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