We compare the precursory behaviour of crustal movements with electromagnetic signatures for the 2011 off the Pacific Coast of Tohoku earthquake. First, we present the Global Positioning System (GPS) data on the co-seismic variations and pre-seismic precursors (medium-term, short-term and imminent precursors). Then, we will review recently published results on electromagnetic precursors, including mainly short-term subionospheric very low frequency (VLF)6 LF propagation anomaly, ultralow frequency (ULF) magnetic field depression and ULF6 extremely low frequency (ELF) atmospheric radiation. Finally, we examine the relationship between the crustal movements and electromagnetic phenomena. We conclude that at least short-term electromagnetic precursors are closely correlated in time with the corresponding crustal movements. This seems to provide evidence on the link between lithospheric and electromagnetic processes. Some discussions will be given on the possible mechanism of this link.
A 98-dimensional feature vector has been proposed to represent temporal characteristics of a waveform of ground motion acceleration on the basis of its Husid plot. Dissimilarity of a pair of waveforms can be quantified in terms of Euclidian distance between corresponding feature vectors. Then a method has been proposed to cluster and classify temporal characteristics of waveforms by use of hierarchical cluster analysis. Illustrative examples using acceleration records observed in the 2011 Off the Pacific Coast of Tohoku Earthquake, Japan are shown. The distribution map of the clustering and classification show that the temporal characteristics affected by the distance from the source region and multiple-source process can be appropriately classified. Multidimensional scaling is also applied to characterize the result of clustering and classification. It is shown that hierarchical cluster analysis is capable of reflecting temporal characteristics better than significant duration.
Effective stress based finite element analyses were carried out by the program code "LIQCA" to compare the damage of the river dike by different earthquake motions. The simulated results of three different earthquake motions ware compared in detail. As the results, it was confirmed that the duration time and the acceleration amplitude of earthquake motion were key factors which affect the damage of the river dike.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.