We apply seismic interferometry to strong-motion records to detect the change in anisotropy caused by the MW 9.0 Tohoku-Oki earthquake on 11 March 2011. It is known that large earthquakes change fluid condition in cracks, and thereby the polarization-anisotropy condition. The Tohoku-Oki earthquake increased the difference between fast and slow shear-wave velocities arising from shearwave splitt...

ABSTRACT This paper presents results of a study of some of the characteristics of a PDR-1 digital strong-motion accelerograph. Results are presented for laboratory tests of the background noise level of the instrument, and these results are compared with previously reported observations for optical instruments. Noise levels for the digital instrument are found to be one or two orders of magnitu...

Boosting is an iterative ensemble-learning paradigm. Every iteration, a weak predictor learns a classification task, taking into account performance achieved in previous iterations. This is done by assigning weights to individual records of the dataset, which are increased if the record is misclassified by the previous weak predictor. Hence, subsequent predictors learn to focus on problematic r...

Fling-step and forward directivity are two important characteristics of near-field earthquakes. Forward directivity occurs when the rupture propagates toward the site and arises in fault‐normal direction for strike‐slip faults. Fling-step is the consequence of permanent ground displacement imposed by near-field earthquakes and arises in strike-slip faults in the strike parallel direction. Fling...

One of the methods for retrofitting reinforced concrete moment frames is the use of steel braces. In this research, the seismic performance of a double-skinned concrete framing system reinforced with two concentric (CBF) and eccentric (EBF) steel bracing, was investigated under seven near-fault earthquake records of varying intensity. For this purpose, two ten-story concrete frames with five sp...

The existence of recorded accelerograms to perform dynamic inelastic time history analysis is of the utmost importance especially in near-fault regions where directivity pulses impose extreme demands on structures and cause widespread damages. But due to the scarcity of recorded acceleration time histories, it is common to generate proper artificial ground motions. In this paper an alternative ...

quake was caused by left-lateral strike-slip motion along a vertical fault plane with dimensions of 20 by 10km striking in the N30°W direction. The strong-motion records from five JMA stations within a distance of 80km are compared with the synthetic seismograms computed from dynamic dislocation models. The comparison yields estimates for the seismic moment, average fault displacements, rise ti...

We board the problem of creating a seismic alert system, based upon artificial neural networks, trained by using the well-known back-propagation and genetic algorithms, in order to emit the alarm for the population located into a specific city, about an eminent earthquake greater than 4.5 Richter degrees, and avoiding disasters and human loses. In lieu of using the propagation wave, we employed...

Several studies have been oriented to develop methodologies for estimating inelastic response of structures; however, the estimation of inelastic seismic response spectra requires complex analyses, in such a way that traditional methods can hardly get an acceptable error. In this paper, an Artificial Neural Network ANN model is presented as an alternative to estimate inelastic response spectra ...

By using seismic records of the 2004 magnitude 6.0 Parkfield earthquake, we identified a burst of high-frequency seismic radiation that occurred about 13 kilometers northwest of the hypocenter and 5 seconds after rupture initiation. We imaged this event in three dimensions by using a waveform back-projection method, as well as by timing distinct arrivals visible on many of the seismograms. The ...