Synthetic uniform-hazard site specific response spectrum

A stochastic model, nonlinear site response computations, and Monte Carlo statistics are incorporated into a process which is used to synthesize the uniform-hazard site specific response spectrum. This procedure, termed the SvE procedure, uses the Monte Carlo process for simulating the seismicity in the seismic areas neighboring the investigated site and to quantify the source parameters of the earthquakes in the simulated catalogues.Stochastic simulations are then applied to each of the listed earthquakes to generate the synthetic S-wave ground accelerations. For sites which are composed of thick layers of soil, each of the synthesized accelerograms is corrected for the nonlinear response of the site. The synthetic free surface S-wave accelerations are used to compute the response spectra for a given damping.Simple statistical analysis of the obtained spectral amplitudes is applied to determine the response spectrum where each of its determined spectral amplitudes has the same prescribed probability of being exceeded.The SvE procedure is demonstrated by determining the uniform-hazard response spectrum of an arbitrarily chosen site in Israel to which hypothetical, yet realistic, soil properties have been assigned.     

Computerized seismic intensities of recently felt earthquakes in Israel

The traditional process of evaluating seismic intensities from questionnaires is laborious and very subjective. An attempt here is made to introduce computerized processing of questionnaires. This is made possible by modifying the questionnaire forms and developing a computer program that performs the evaluation in a rather objective manner. The prime assumption behind this procedure is that observed intensities in a certain location are normally distributed. This new approach has been tested successfully with recently obtained data on earthquakes in Israel, yielding evaluated intensities and isoseismal maps for earthquakes in the Jordan Valley (January 13, 1982), Lebanon (June 3, 1983), the Gulf of Suez (June 12, 1983), the Jezreel Valley (August 24, 1984), and near Jericho (January 25, 1985).     

Seismic network detection probability assessment using waveforms and accounting to event association logic

The geographical area where a seismic event of magnitude M?≥?M _t is detected by a seismic station network, for a defined probability is derived from a station probability of detection estimated as a function of epicentral distance. The latter is determined from both the bulletin data and the waveforms recorded by the station during the occurrence of the event with and without band-pass filtering. For simulating the real detection process, the waveforms are processed using the conventional Carl Johnson detection and association algorithm. The attempt is presented to account for the association time criterion in addition to the conventional approach adopted by the known PMC method.     

Kinematic multistation discriminator between local quarry blasts and earthquakes

It has long been known that S waves on seismograms of local explosions are often accompanied by strong low-frequency, low-velocity, Rg surface wave trains, often significantly diminished for earthquakes. We utilize this fact to construct a new formal discriminator between earthquakes and explosions by measuring the S -surface-wave group velocity. The method is based on analysing the velogram; that is, the display of the envelope of ground motion versus group velocity V = R/T , where R is the epicentral distance and T  the traveltime. We examine the distribution of seismic energy in time and space using envelopes of records from the Israel Seismic Network (ISN), from which we compute the velograms and observe differences in the velograms of quarry blasts and earthquakes. The data include 143 seismic events occurring in three areas (Galilee, Dead Sea, and Gilad) monitored by the ISN; the magnitude range is M _L = 1.0–2.8 at distances of 15–310 km. From the velograms we measure the group velocity, V _{m s} , within the 1–4 km s⁻¹ range at which the velogram reaches its maximum for each available station. The resulting V _{m s} (R) function is closely fitted by the empirical relationship a + b  ln  R , with a and b coefficients varying from event to event. A simple linear function c = b + 0.33a at a threshold C = 0.69 completely separates ( a,b ) pairs for the 67 Galilee events, and, for the 76 remaining events, one earthquake and four explosions are wrongly classified. After data validation and application of the Fisher linear discriminator, adapted to the events from Galilee, only two misidentified events remain for the whole data set.     

Analysis of thermo-hydrologic-mechanical impact of repository for high-level radioactive waste in clay host formation: an Indian reference disposal system

In our study, a coupled hydrologic-mechanical analysis is done of the excavation damaged zone, before the emplacement of nuclear waste. This is followed by a coupled thermal-hydrologic-mechanical analysis to evaluate the impact of nuclear waste repository in porous water containing rock mass. This analysis has been under taken in accordance with the Indian reference disposal system. The paper considers the changes in pore pressure and stresses due to excavation of disposal holes. A critical study of rock mass permeability, porosity, thermally induced stresses, strains, and temperature distribution after the emplacement of nuclear spent fuels in disposal holes has also been done. Coupling to the mechanical constitutive equations is done via ??effective?? normal strain rates.