An extremely large earthquake (with magnitude of 8.2) happened on 8 August 1993 near the Guam island, and ultra-low-frequency (ULF) (frequency less than 1 Hz) electromagnetic fields were measured by 3-axis induction magnetometers at an observing station (with the epicentral distance of 65 km) with sampling frequency of 1 Hz. In order to study electromagnetic signature of prefracture criticality...

We present a variety of examples, showing systematic fluctuations as a function of angular order of measured eigenfrequencies for given normal modes of the Earth. The data are single station measurements from the CEOSCOPE network. Such fluctuations are attributed to departures from the lowest order asymptotic expression of the geometrical optics approximation. We derive first-order asymptotic e...

[1] PS converted waves observed near Ancona on the Adriatic coast of central Italy, as revealed by teleseismic receiver functions (RFs), vary with earthquake backazimuth and epicentral distance in a manner consistent with a 1-D anisotropic seismic structure. Using reflectivity calculations, we develop a profile of anisotropic seismic velocity through the Adriatic lithosphere at this locality. W...

We analyzed four pairs of a large (Mw "'6) and a small (Mw "' 3.5 to 4) shallow strike-slip earthquakes to investigate the scale-dependence. of the seismic energy-tomoment ratio, an important macroscopic parameter which reflects the basic physical process of seismic slip. These earthquakes occurred in the south-western part of Japan, and high-quality close-in records (epicentral distance< 50 km...

-Travel times of waves generated by an earthquake at a depth of 600 km and reflected from the inside of the core boundary as well as the epicentral distances of the caustics of PKKP, SKKP, and PKKS agree within the limits of error with those calculated on the basis of velocity-depth curves. This applies also to the travel times of SKKS and SKKKS for which poor agreement was reported before the ...

The advent of GPS provided a new way measuring surface displacements due to earthquakes by deploying networks within active seismic areas. Japan is located in the confluence several tectonic plates, hence its seismicity. In order surveille this activity, one wider network world was deployed, i.e., GEONET. By processing data from 93 GEONET reference stations, we analyze 2011 Tohoku-Oki earthquak...

The nationwide strong-motion seismograph network of K-NET and KiK-net in Japan successfully recorded the strong ground motions of the 2016 Kumamoto earthquake sequence, which show the several notable characteristics. For the first large earthquake with a JMA magnitude of 6.5 (21:26, April 14, 2016, JST), the large strong motions are concentrated near the epicenter and the strong-motion attenuat...

This study reviews seismograms from 10 rock-fall events recorded between 1992 and 2001 by the permanent seismological network Sismalp in the French Alps. A new seismic magnitude scale was defined, which allowed us to compare and classify ground-motion vibrations generated by these Alpine rock-falls. Each rock-fall has also been characterized by its ground-motion duration t30 at an epicentral di...

ground vibrations during an earthquake can severely damage structures and equipments housed in them. many factors including earthquake magnitude, distance from the fault or epicenter, duration of strong shaking, soil condition of the site, and the frequency content of the motion define the properties of ground motion and its amplification. a deep understanding of the effects of these factors on...