[en] It is widely known that, before a tsunami attacked a coast, loud sounds like thunders were heard in coastal areas and/or vessels in the ocean felt sea shocks. Sea shocks are violent shocks with long durations felt by ocean vessels at the moment of submarine earthquakes. The cause of sea shocks is thought to be the T phase. Tsunami-producing earthquakes, large and shallow focus seismic events occurring at sea can generate the T phase, that is, seismic waves generated by their conversion at an ocean bottom, propagate over large distance at the speed of the sound wave in the sea water along the SOFAR channel. Many studies have been done about the use of the T phase for tsunami warnings. For example, in this paper, considering the compressibility of the sea water, it is shown that another mechanism can also generate the low frequency T phase. It is also shown that the low frequency T phase carries the information of the magnitude and the duration of the displacement of the ocean bottom and is useful for tsunami warnings, in particular, for near shore tsunami warnings. 3 refs, 8 figs

No abstract available

[en] Definitions, methods of measurement, and recommendations for the performance of deformation measurements in nuclear power stations are given. (TK/AK)

[en] It is presented a procedure to identify the incompleteness of a seismic catalogue which is an enhancement of a method previously developed and applied by us. It consists of three steps: aftershock and swarm removal, measure of the relative completeness, and estimate of the absolute completeness. It has been assumed that the independent events form a stationary Poisson process and taken the nonstationarities of the recorded seismic sequences as a measure of relative completeness. Under the further assumption that the subcatalog consisting of the largest events which occurred most recently is absolutely complete, it is possible to evaluate the true occurrence rate for all magnitudes. The sequence of earthquakes which occurred in Calabria and Sicily is analysed and the results are compared with those previously obtained

[en] For the simulation of the reference ground motion, the distribution of the amplitudes over the total duration, as well as, the strong motion duration characteristics are required. The intensity function and the strong motion duration depend on various parameters, such as earthquake magnitude, crack pattern of the source, path of the propagation of seismic waves, distance to the source, local subsurface conditions. Moreover, not only the body waves, but also the contribution of the surface waves may have to be considered in some cases. Due to the randomness of the parameters involved in earthquake motions a probabilistic consideration of the problem has been conducted. The duration characteristics of both horizontal and vertical components of strong earthquake motions have been obtained. Four different kinds of deterministic intensity function have been developed. (orig./HP)

[en] This document comprises the essential elements of an earthquake resistant design code for nuclear facilities with limited radioactive inventory. The purpose of the document is the enhancement of seismic safety for such facilities without the necessity to resort to complicated and sophisticated methodologies which are often associated with and borrowed from nuclear power plant analysis and design. The first two sections are concerned with the type of facility for which the document is applicable and the radiological consideration for accident conditions. The principles of facility classification and item categorization as a function of the potential radiological consequences of failure are given in section 3. The design basis ground motion is evaluated in sections 4-6 using a simplified but conservative approach which also includes considerations for the underlying soil characteristics. Sections 7 and 8 specify the principles of seismic design of building structures and equipment using two methods, called the equivalent static and simplified dynamic approach. Considerations for the detailing of equipment and piping and those other than for lateral load calculations, such as sloshing effects, are given in the subsequent sections. Several appendices are given for illustration of the principles presented in the text. Finally, a design tree diagram is included to facilitate the user's task of making the appropriate selections. (author)

[en] A series of sensitivity analyses for multi-story base-isolated structures subject to a harmonic ground excitation is carried out. Several base isolation and energy dissipation devices are considered. The effects of variations in properties of structures and base-isolation systems on the peak responses are studied. For a range of natural frequency, friction coefficient, and damping of the isolator, the peak responses are evaluated. The sensitivity of the base-isolated structure to variations in the amplitude and the frequency of ground excitation is also studied. Particular attention is given to the effects of long-period excitations. The study shows that the peak structural responses for base isolators with a frictional element are less sensitive to variations in intensity and frequency of ground excitation when compared with non-frictional systems. Furthermore, the performances of frictional isolators are insensitive to small variations in friction coefficient and its velocity-dependence. (orig.)

[en] This article reviews earthquake vibratory ground-motion intensity-distance-attenuation relationships and depicts the evolution and limitations of currently used procedures for predicting the rate of attenuation of intensity of vibratory ground motion with respect to distance from the earthquake source. Two general procedures are considered: one procedure relates peak horizontal ground acceleration, earthquake magnitude, and distance; the other relates epicentral modified Mercalli intensity (MMI), distance, and attenuated MMI. A conversion relationship between MMI and peak horizontal ground acceleration is used with the latter. Using the procedures, conclusions are drawn regarding the relative validity of various ground-motion attenuation relationships in various soils

[en] Fault model has been developed to estimate a strong ground motion in consideration of characteristics of seismic source and propagation path of seismic waves. There are two different approaches in the model. The first one is a theoretical approach, while the second approach is a semi-empirical approach. Though the latter is more practical than the former to be applied to the estimation of input motions, it needs at least the small-event records, the value of the seismic moment of the small event and the fault model of the large event

[en] The study reveals an important correlation between phase properties of an earthquake strong motion and its characteristic features, especially between either the phase angles or the phase differences and the amplitudes of motion varying associated with the lapse of time within duration of motion. A real earthquake waveform of the SOOE component obtained at El Centro, California during the Imperial Valley earthquake of 1940 is taken for the strong motion waveform specified for synthetic simulation. (orig./HP)