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Time-averaged shear wave velocity over the upper 30 m of the earth’s surface ( V S30) is a key parameter for estimating ground motion amplification as both a predictive and a diagnostic tool for earthquake hazards. The first-order approximation of V S30 is commonly obtained through a topographic slope–based or terrain proxy due to the widely available nature of digital elevation models. However, better-constrained V S30 maps have been developed in many regions. Such maps preferentially employ various combinations of V S30 measurements, higher-resolution elevation models, lithologic, geologic, geomorphic, and other proxies and often utilize refined interpolation schemes. We develop a new hybrid global V S30 map database that defaults to the global slope-based V S30 map, but smoothly inserts regional V S30 maps where available. In addition, we present comparisons of the default slope-based proxy maps against the new hybrid version in terms of V S30 and amplification ratio maps, and uncertainties in assigned V S30 values.

The Mackenzie Mountains EarthScope Project—a collaboration between Colorado State University, the University of Alaska, Michigan State University, and Yukon College—deployed a roughly linear, 40-station broadband seismographic network. This network crossed the actively deforming Northern Canadian Cordillera and the Mackenzie Mountains in Yukon, Canada; it also extended into the Canadian Shield in Northwest Territories, Canada. The array was deployed between July 2016 and August 2018 (with four pilot stations installed in July 2015 and three extended stations operating through August 2019) coinciding with and complementing the deployment of the EarthScope Transportable Array to Alaska and western Canada. In this article, we present an overview of project scientific objectives, station configurations, and site conditions; discuss environmental challenges, including those that resulted in station downtime (e.g., spring flooding and encounters with bears); and suggest potential solutions to such subarctic challenges for the benefit of future deployments in comparable regions. We also include an initial characterization of seasonal and geographic variations in ambient seismic noise for the northwestern Canadian Cordillera.

A typical seismic experiment involves installing 10–50 seismometers for 2–3 yr to record distant and local earthquakes, along with Earth’s ambient noise wavefield. The choice of the region is governed by scientific questions that may be addressed with newly recorded seismic data. In most experiments, not all stations record data for the full expected duration. Data loss may arise from defective equipment, improperly installed equipment, vandalism or theft, inadequate power sources, environmental disruptions (e.g., snow covering solar panels and causing power outage), and many other reasons. In remote regions of Alaska and northwestern Canada, bears are a particular threat to seismic stations. Here, we document three recent projects (Southern Alaska Lithosphere and Mantle Observation Network, Fault Locations and Alaska Tectonics from Seismicity, and Mackenzie Mountains EarthScope Project) in which bears were regular visitors to remote seismic stations. For these projects, there were documented bear encounters at 56 out of 88 remote stations and 6 out of 85 nonremote stations. Considering bear‐disrupted sites—such as dug‐up cables or outages—there were 29 cases at remote stations and one case at nonremote stations. We also compile bear encounters with permanent stations within the Alaska Seismic Network, as well as stations of the Alaska Transportable Array. For these two networks, the stations are designed with fiberglass huts that house and protect equipment. Data losses at these networks because of bears are minor (

An algorithm is proposed for the discrete approximation of continuous market price processes that uses trees instead of lattices. It is shown that it is convergent when used for pricing both European and American options and that it is more efficient, for some models, than the usual recombining schemes.

Safety studies for existing dams have found that some do not satisfy current estimates of the probable maximum flood (PMF). An event or influence diagram can describe the random factors that contribute to major inflow floods and that determine reservoir operation and possible downstream damages during a flood event. This allows calculation of the probability of dam failure and the distributions of damages and loss of life using combinations of various analytical and Monte Carlo methods. This paper discusses the efficiency of different evaluation methods: event trees, simple Monte Carlo sampling, Latin hypercube sampling, importance sampling, and a analytical/stratified Monte Carlo (A/SMC) method. The analysis suggests that the A/SMC method and importance sampling have great potential for the efficient estimation of dam failure risks. Numerical examples employ the distributions of damages and loss of life to show the character of trade-offs presented by many dam safety decisions and illustrate problems with the partitioned multiobjective risk method (PMRM). The use of partial expected damage and loss of life functions is recommended to show the importance of low-probability/high-consequence events.

This report documents an application of risk analysis techniques to dam safety analysis. The research contributes to the evolution of risk-based dam safety assessment methods by illustrating how such analyzes might be improved. The study examines the employment of detailed stochastic descriptions of the rainfall and runoff processes, and performance improvements in warning systems, dams, and other structures. Using a detailed stochastic analysis concerning hydrologic risk will give decision-makers more information about the implications of adopting alternative solutions to dam safety problems. The analysis herein presented is not advocating the use of risk analysis in lieu of traditional design standard analysis for project decision-making. Rather, it proposes the use of quantitative risk analysis as a complement to current design standard analysis practices.

An abstract gambler's problem is formulated in a continuous-time setting and analogues are proved for some of the discrete-time results of Dubins and Savage in their book How to Gamble if You Must. Applications are made to problems of controlling a Brownian motion process.