Strain-Dependence of Surface Diffusion: Ag on Ag(111) and Pt(111)

Using density-functional theory with the local-density approximation and the generalized gradient approximation we compute the energy barriers for surface diffusion for Ag on Pt(111), Ag on one monolayer of Ag on Pt(111), and Ag on Ag(111). The diffusion barrier for Ag on Ag(111) is found to increase linearly with increasing lattice constant. We also discuss the reconstruction that has been found experimentally when two Ag layers are deposited on Pt(111). Our calculations explain why this strain driven reconstruction occurs only after two Ag layers have been deposited.Comment: 4 pages, 3 figures, Phys. Rev. B 55 (1997), in pres

Locations of small earthquakes near the trifurcation of the San Jacinto fault southeast of Anza, California

About 100 small earthquakes (M ≈ 1/2 to 2) which occurred near the trifurcation of the San Jacinto fault southeast of Anza, California, have been accurately located using five- and six-station arrays with dimensions of about 10 km. The pattern of epicenters is complex and extends several km outside of the area outlined by the traces of faulting. Patterns of seismicity observed on opposite sides of the San Jacinto fault are significantly different. On the southwest side, a concentration of foci lies at a depth of about 4-7 km along the projected extension of the Coyote Creek fault a few km northwest of the last surface evidence of faulting. On the northeast side, earthquakes are concentrated at depths between 10 and 15 km. A group of the latter events recorded about 1 week after the magnitude 4.7 earthquake of May 21, 1967 forms a linear pattern parallel to the San Jacinto fault with depths from 3 to 15 km. This pattern may represent the zone of energy release or slip for that earthquake and possibly the plane of the San Jacinto fault at depth, although the epicenters are located about 2 to 3 km to the northeast of the trace of the San Jacinto fault. Most of the earthquakes located in this study are not aftershocks in the usual sense, i.e., easily correlated with a preceding large earthquake. They represent a complex pattern of seismicity which has continued at least for the last 3 years on the micro-earthquake level and for the last 30 years on the macroseismic level

Reply to Comment by J. Zhang and N. Makris on “Estimates of the Ground Accelerations at Point Reyes Station during the 1906 San Francisco Earthquake” by A. Anooshehpoor, T. H. Heaton, B. Shi, and J. N. Brune

Contrary to the comments by Zhang and Makris (hereafter, ZM), our equations of motion governing the rocking response of a rectangular block subjected to a full-sine acceleration pulse are correct. Therefore, the first part of ZM's discussion, which is based primarily upon the assumption that the equations of motion in our article were incorrect, is inappropriate. In the second part of the discussion, ZM present new results for mode 2, toppling without impact. We did not consider this mode because it was not relevant to the Point Reyes train, which by eyewitness accounts, had overturned after experiencing one impact. However, as explained in this reply, toppling with no impact is never the minimum condition for overturning, and would in general involve very large horizontal accelerations, especially at frequencies where mode 2 is the only overturning mode

Test of nuclear level density inputs for Hauser-Feshbach model calculations

The energy spectra of neutrons, protons, and alpha-particles have been measured from the d+59Co and 3He+58Fe reactions leading to the same compound nucleus, 61$Ni. The experimental cross sections have been compared to Hauser-Feshbach model calculations using different input level density models. None of them have been found to agree with experiment. It manifests the serious problem with available level density parameterizations especially those based on neutron resonance spacings and density of discrete levels. New level densities and corresponding Fermi-gas parameters have been obtained for reaction product nuclei such as 60Ni,60Co, and 57Fe

Precarious Rock Methodology for Seismic Hazard: Physical Testing, Numerical Modeling, and Coherence Studies

The precarious rock methodology used for seismic hazard assessment includes location, age dating, field measurements of the quasi-static toppling acceleration of balanced rocks, and study of their dynamic response to realistic strong motion seismograms using numerical modeling. The work scope is contained in the task description issued by the DOE to the Seismology Laboratory of the University of Nevada, Reno and is itemized in section 2.3 below. In addition, measurement of the coherence of seismic energy at high frequencies, critical to the understanding of the variability of high frequency ground motions at the repository level, will be estimated based on data collected in limited scope portable instrument deployments. Existing high-frequency geophones that remain in place from earlier geophysical experiments will be used

Initial borehole accelerometer array observations near the north portal of the ESF

This report addresses observed ground motions at the site of the proposed surface facilities associated with the designated repository for high-level nuclear waste at Yucca Mountain, Nevada. In 2003 an accelerometer array was installed at three boreholes on the pad of the north portal of the ESF (Exploratory Studies Facility) at Yucca Mountain, Nevada, by the Nevada Seismological Laboratory (NSL). These boreholes, roughly 150 m apart and initially used for extensive geological and geophysical surveys, were ideal locations to measure the subsurface ground motions at the proposed site of surface facilities such as the Waste Handling Building. Such measurements will impact the design of the facilities. Accelerometer emplacement depths of approximately 15 m from the surface and then at the bottom of the boreholes, roughly 100 m, were chosen. Accelerometers were also placed at the surface next to the boreholes, for a total of nine accelerometers, all three-component. Data recording was accomplished with onsite recorders, with the onsite data transmitted to a central computer at a trailer on the pad. All requirements were met to qualify these data as “Q”. Due to the lack of significant recordings during 2003, several low signal-to-noise (S/N) quality events were chosen for processing. The maximum horizontal peak ground acceleration (PGA) recorded at the pad was approximately 1 cm/s2 in 2003;the corresponding peak ground velocity (PGV) was approximately 0.01 cm/s. PGA and PGV were obtained at all nine accelerometers for most of these events, and spectra were computed. Ground motion amplitudes varied significantly across the boreholes. Higher ground amplifications were observed at the surface for the two boreholes that penetrated a thick amount (~ 30 m) of fill and Quaternary alluvium compared to the one that had less than 2 m of such. Additionally, surface-to-deep recordings showed as much as a factor of five amplification at these two boreholes. Signal correlation with inter-borehole distance agrees with basic Initial Borehole Accelerometer Array Observations Near the North Portal of the ESF Page 6 of 87 scattering theory, and the recorded signals across the wavefront correlate more strongly than those along the propagation path. Transfer functions computed from layered models for each borehole reflect some of the actual signal attributes fairly well, but many more signals need to be recorded and used to provide a good basis of comparison

Extreme Ground Motion Studies

This project consists of two separate investigations into extreme ground motions due to seismic events. First, it includes field studies of geological formations that should put an upper bound on extreme ground motions that have happened at the site of the formations. The locations are critically selected to provide the most effective constraints possible on the validity of the probabilistic seismic hazard analysis for Yucca Mountain. Second, this project surveys recorded ground motions from around the world, and aims to draw general conclusions from these as to the conditions where extreme ground motions are observed

Modelling the Recoherence of Mesoscopic Superpositions in Dissipative Environments

A model is presented to describe the recently proposed experiment (J. Raimond, M. Brune and S. Haroche Phys. Rev. Lett {\bf 79}, 1964 (1997)) where a mesoscopic superposition of radiation states is prepared in a high-Q cavity which is coupled to a similar resonator. The dynamical coherence loss of such state in the absence of dissipation is reversible and can in principle be observed. We show how this picture is modified due to the presence of the environmental couplings. Analytical expressions for the experimental conditional probabilities and the linear entropy are given. We conclude that the phenomenon can still be observed provided the ratio between the damping constant and the inter-cavities coupling does not exceed about a few percent. This observation is favored for superpositions of states with large overlap.Comment: 13 pages, 6 figure

A Long Baseline Laser Strainmeter for the Exploratory Studies Facility at Yucca Mountain

This Scientific Investigation Plan (SIP), for work under the second Department of Energy/University and Community College System of Nevada (DOE/UCCSN) Cooperative Agreement (10/01/03), DEFC28- 04RW12232, is intended to cover the laser strainmeter operation and monitoring task being conducted by the University of California, San Diego (UCSD), under the oversight of the Nevada Seismological Laboratory of the University of Nevada-Reno (NSL/UNR). UCSD has carried out the design, engineering, and installation of the east-west laser strainmeter (LSM) currently in place in the Exploratory Studies Facility (ESF) at Yucca Mountain