A study on the duration of strong earthquake ground motion

A simple definition of the duration of strong earthquake ground motion based on the mean-square integral of motion has been presented. It is closely related to that part of the strong motion which contributes significantly to the seismic energy as recorded at a point and to the related spectral amplitudes. Correlations have been established between the duration of strong-motion acceleration, velocity, and displacement and Modified Mercalli intensity, earthquake magnitude, the type of recording site geology, and epicentral distance. Simple relations have been presented that predict the average trend of the duration and other related parameters as a function of Modified Mercalli intensity, earthquake magnitude, site geology and epicentral distance

On the correlation of seismic intensity scales with the peaks of recorded strong ground motion

Correlations of the recorded peak acceleration, velocity and displacement, and the Modified Mercalli intensity have been carried out for 57 earthquakes and 187 strong-motion accelerograms recorded in the Western United States. Correlations of peak acceleration with intensity, characterized by the data scatter exceeding one order of magnitude, have lead to average peak accelerations which are higher than those reported by a majority of previous investigators. New correlations, also characterized by scatter of data of about one order of magnitude, have been presented for peak velocities and displacements of strong ground motion versus Modified Mercalli intensity. Grouping of all recorded data according to the geology underlying the strong-motion accelerograph stations was carried out and permitted a study of the possible effects that local geology might have on the peaks of strong-motion acceleration, velocity, and displacement. Results of this analysis are as follows: (1) For ground shaking of a particular Modified Mercalli intensity, average peak acceleration recorded on hard rock is higher by a factor less than about two than the average peak acceleration recorded on alluvium; (2) the effect of local geology on the average peak velocity leads to marginally higher peak values on alluvium; and (3) the peak ground displacements are larger, by a factor less than two, when recorded on alluvium rather than on hard rock

On correlation of seismoscope response with earthquake magnitude and Modified Mercalli Intensity

A quantitative measure of the Modified Mercalli Intensity Scale for earthquakes in the western United States has been developed by correlating the peak seismoscope relative displacement response, S_d, with the reported site intensity, I_(MM). This correlation can be approximated by S̄_d(cm) ≈ 1/49.2(10^(0.288 I_MM)) for I_(MM) ≦ VIII and is characterized by one standard deviation of about 0.7 S̄_d. The data used in this study do not indicate an obvious type of dependence of S_d on local site conditions. A method for computing the analog of the local earthquake magnitude, M_(seismoscope), has been presented for possible use in strong-motion seismology and for scaling earthquakes by close-in measurements, when other seismological instruments may go off scale

Radical ions and excited states in radiolysis. Optically detected time resolved EPR

Excited-state production and radical-ion recombination kinetics in pulse-irradiated solutions of aromatic solutes in cyclohexane are studied by a new method of optical detection of time-resolved electron paramagnetic resonance (EPR) spectra. 7 figures

Pulse radiolysis of liquid water using picosecond electron pulses produced by a table-top terawatt laser system

A laser based electron generator is shown, for the first time, to produce sufficient charge to conduct time resolved investigations of radiation induced chemical events. Electron pulses generated by focussing terawatt laser pulses into a supersonic helium gas jet are used to ionize liquid water. The decay of the hydrated electrons produced by the ionizing electron pulses is monitored with 0.3 μs time resolution. Hydrated electron concentrations as high as 22 μM were generated. The results show that terawatt lasers offer both an alternative to linear accelerators and a means to achieve subpicosecond time resolution for pulse radiolysis studies. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69949/2/RSINAK-71-6-2305-1.pd

Radical Cations in Radiation Chemistry of Liquid Hydrocarbons

The state of knowledge concerning radical cations in liquid alkanes is discussed with particular emphasis on those which exhibit high mobility. Uncertainty has existed in the interpretation of previous results with respect to the nature and reactivity of high mobility ions, especially for cyclohexane. Recent time-resolved studies on pulse radiolysis/transient absorption, photoconductivity, and magnetic resonance in these systems have led us to propose new mechanisms for the high mobility ions. In decalins, scavenging of these ions by solutes is a pseudo-first-order reaction. In cyclohexane, the behavior is more complex and is indicative of the involvement of two species. This bimodality is rationalized in terms of a dynamic equilibrium between two conformers of the solvent radical cation. Several experimental tests supporting these views include a recent study on two-color laser photoionization in cyclohexane

Synthesis of accelerograms compatible with the Chinese GB 50011-2001 design spectrum via harmonic wavelets: artificial and historic records

A versatile approach is employed to generate artificial accelerograms which satisfy the compatibility criteria prescribed by the Chinese aseismic code provisions GB 50011-2001. In particular, a frequency dependent peak factor derived by means of appropriate Monte Carlo analyses is introduced to relate the GB 50011-2001 design spectrum to a parametrically defined evolutionary power spectrum (EPS). Special attention is given to the definition of the frequency content of the EPS in order to accommodate the mathematical form of the aforementioned design spectrum. Further, a one-to-one relationship is established between the parameter controlling the time-varying intensity of the EPS and the effective strong ground motion duration. Subsequently, an efficient auto-regressive moving-average (ARMA) filtering technique is utilized to generate ensembles of non-stationary artificial accelerograms whose average response spectrum is in a close agreement with the considered design spectrum. Furthermore, a harmonic wavelet based iterative scheme is adopted to modify these artificial signals so that a close matching of the signals’ response spectra with the GB 50011-2001 design spectrum is achieved on an individual basis. This is also done for field recorded accelerograms pertaining to the May, 2008 Wenchuan seismic event. In the process, zero-phase high-pass filtering is performed to accomplish proper baseline correction of the acquired spectrum compatible artificial and field accelerograms. Numerical results are given in a tabulated format to expedite their use in practice