Annual Probability Of Occurrence Research Articles

Theoretical Boundaries of Annual Flood Risk for Single-Family Homes Within the 100-Year Floodplain

Special flood hazard areas (SFHAs), defined as having an annual probability of occurrence of 1 percent or above, are used by U.S. Federal Emergency Management Agency (FEMA) to demarcate areas within which flood insurance purchase is required to secure a mortgage. However, quantifying flood risk within SFHAs can be challenging due to the lack of modeled flood depth data for all return periods. To address this issue, this research quantifies flood risk indicated by average annual loss (AAL) within the A Zone—the subset of the SFHA where wave heights can potentially range from 0 to 3 feet. The methodology resolves the Gumbel quantile function for four distinct flooding cases (i.e., locations flooded at return periods exceeding 1.58-, 10-, 25-, and 50-year return period events) and generates synthetic flood hazard parameters for these cases within the 100-year floodplain, as well as with additional elevation above the base flood elevation (BFE), known as freeboard, for single-family homes with different attributes. The results indicate that for single-family homes in the A Zone, with the lowest floor elevated to the BFE, the AAL ranges from 0.3 to 1 percent of the building replacement cost value. Adding one foot of freeboard reduces flood risk by over 90% if the annual flood risk is between the minimum and 25th percentiles and the 100-year flood depth is less than two feet. The demonstrated approach helps enhance flood resilience in the A Zone, demonstrating the feasibility of proactive measures to protect communities.

Seismic response analysis of super-high-rise building structures with three-layer isolation systems

This paper proposes a triple-layer isolation device based on the single-story isolation and double-layer isolation. By establishing dynamic equilibrium equations and conducting earthquake response comparative analyses on the same super-tall building structure using three different forms of isolation: single-story isolation, double-layer isolation, and triple-layer isolation, it is found that the triple-layer isolation device, which adds an isolation layer on the basis of the double-layer isolation device, exhibits many different characteristics in terms of its damping mechanism, seismic response rules, etc., due to the differences in the position and quantity of the isolation layer. Rare earthquakes are equivalent to ASCE maximum considered earthquake or annual occurrence probability of 2%. The research shows that, under rare earthquake conditions, the isolation effect of the triple-layer isolation device in the super-tall frame-shear structure is better than that of the single-story isolation and double-layer isolation devices. Particularly, as the number of floors increases, the triple-layer isolation device can significantly reduce the seismic isolation support tension and compression stresses, inter-story displacement, single-story shear force, overturning moment, and floor acceleration of the high-rise building structure, and concentrate the lateral displacement of the structure on the three isolation layers, dissipating most of the seismic input energy.

The duality of drought: Pelagic‐ and benthic‐spawning stream fishes show opposing responses to drought in the southern Great Plains

AbstractObjectiveStreamflow is a primary determinant of fish assemblage structure in riverine systems, but alteration of natural flow regimes can result in fish assemblage shifts through the process of environmental filtering. Because natural drought conditions reduce and homogenize streamflow in a manner comparable to projections for climate change in some regions, drought could serve as a proxy for expected future flow conditions.MethodsWe investigated the effects of drought as a temporally dynamic environmental filter of the occurrence of two guilds of fishes, benthic spawners that deposit adhesive ova along the benthic zone of rivers and pelagic spawners that release semibuoyant, nonadhesive ova into the pelagic zone of rivers. We developed species‐specific random forest models to estimate annual probability of occurrence for three benthic‐spawning and four pelagic‐spawning minnow species at three sites in the upper Brazos River, Texas, for the period 1950–2018. We then used a generalized additive mixed‐effects model to assess the relationship between drought intensity and likelihood of occurrence to test whether reproductive modes differed in response to drought (hypothesis 1) and whether response to drought was spatially (hypothesis 2) or temporally (hypothesis 3) variable.ResultWe found support for hypothesis 1 as two of four pelagic‐spawning species (Shoal Chub Macrhybopsis hyostoma, Smalleye Shiner Notropis buccula) declined and two of three benthic‐spawning species increased as drought intensified, support for hypothesis 2 as responses to drought varied by gauge location, and no support for hypothesis 3 as drought response was consistent for periods 1950–1979 and 1980–2018.ConclusionThese findings offer insight into the future of riverine fish assemblages as climate change is expected to exacerbate regional drought conditions. Management of pelagic‐spawning fishes during extreme drought in the southern Great Plains may require strategies such as (1) rescues of fish from drying reaches, (2) captive holding and propagation, and (3) assisted recolonization following subsidence of drought conditions.

A hybrid Monte Carlo simulation risk model for oil exploration projects

A new 3-D Hybrid Monte Carlo Simulation (MCS) Risk Model is proposed in this study. The wind, wave, current, climate change, and tsunami sub-models of the Three-Dimensional Hydrodynamic Transport and Water Quality Model HYDROTAM-3D are interrelated with MCS, to obtain probability distributions for the simulation of environmental conditions. This is the only model that can incorporate the tsunami, storm, and sea level rise risks in oil exploration projects. The spill risk index (SRI) of 50 blue barrels spilled due to a blowout from the rig/port during fuel supply was circa 1 ton/ship as Tier I with an average annual occurrence probability of 1.0 × 10−6. The discharge of 4000 bbls for 6 h was modeled, resulting in the SRI of 546 metric tons from the riser blowout with SRI = 0.2 per meter, indicating a Tier II risk. The mean arrival time of this spill was found by MCS as 145 min.

Increasing sequential tropical cyclone hazards along the US East and Gulf coasts

Two tropical cyclones (TCs) that make landfall close together can induce sequential hazards to coastal areas. Here we investigate the change in sequential TC hazards in the historical and future projected climates. We find that the chance of sequential TC hazards has been increasing over the past several decades at many US locations. Under the high (moderate) emission scenario, the chance of hazards from two TCs impacting the same location within 15 days may substantially increase, with the return period decreasing over the century from 10–92 years to ~1–2 (1–3) years along the US East and Gulf coasts, due to sea-level rise and storm climatology change. Climate change can also cause unprecedented compounding of extreme hazards at the regional level. A Katrina-like TC and a Harvey-like TC impacting the United States within 15 days of each other, which is non-existent in the control simulation for over 1,000 years, is projected to have an annual occurrence probability of more than 1% by the end of the century under the high emission scenario.

Quantifying annual occurrence probability of rainfall-induced landslide at a specific slope

Although many countries and regions (e.g., Australia, the Netherlands, Hong Kong) have adopted risk assessment and management methods for landslide risk mitigation, a conventional method based on factor of safety (FS), instead of annual failure probability, is widely used in existing practice of slope engineering. It remains challenging for geotechnical practitioners to assess quantitatively annual failure probability and landslide risk of a specific slope, hindering implementation of landside risk assessment and mitigation in practice. This study proposes an innovative yet practical method to assess quantitatively annual failure probability of a site-specific slope caused by rainfall infiltration. The proposed method integrates slope stability analysis currently used in geotechnical practice with rainfall infiltration into the slope and annual exceedance probability of rainfall to obtain explicit relationships for estimation of the annual failure probability. The quantified annual failure probability comprehensively reflects possible rainfall patterns to the slope, and model settings and soil properties used in slope seepage and stability analyses. It can be implemented conveniently in geotechnical practice through a repeated execution of conventional slope seepage and stability analyses. The proposed method is illustrated by a real slope example in Hong Kong for calculating the annual failure probability of the slope before and after slope retrofitting.

A proposed criteria to identify wind turbine drivetrain bearing loads that induce roller slip based white-Etching cracks

In this article, the type of roller slip behavior that may result in the formation of white-etching cracks (WECs) in wind turbine gearbox bearings is identified. A new hypothesis based on the inner raceway normal contact load magnitude at the time of roller slip is proposed as the probable cause of WECs. For this purpose, the maximum normal contact loads are identified when roller slip occurs in high-speed shaft bearings at different mean wind speeds. Subsequently, the annual probability of occurrence of the maximum normal loads are obtained. The probability of maximum load under slip exceeding a limit probability is hypothesized as a probable cause for WEC. In order to apply the proposed hypothesis, two different wind turbines high-speed shaft bearings are used: the cylindrical roller bearing of the General Electric 1.5 SLE turbine and the tapered roller bearing of Vestas V52 turbine. Both the chosen bearings are on the generator side of the high-speed shaft. For both turbines, measurement data together with analytical models are used for identifying the slip and the maximum normal contact loads. We propose forecasting the probability of exceedance of a threshold maximum normal contact load level during slip to identify the possibility for inducing WECs.

Characterization and Liquefaction Hazard Assessment of Two Hungarian Liquefied Sites from the 1956 Dunaharaszti Earthquake

The seismicity of Hungary can be considered moderately active, nevertheless contemporary reports from the past approx. 350 years documented surface manifestations of liquefaction occurrences. The last such earthquake was the 1956 Dunaharaszti ground motion, for which the location of two liquefied sites could be identified approx. 60 years after the event. This provided an excellent opportunity to analyze possibly the only accessible liquefied sites in Hungary. Analysis of the two sites included field and laboratory tests allowing the back-calculation of maximum horizontal ground acceleration of the earthquake. This parameter was previously unknown because the closest seismometer saturated during the event. The performed back-analysis using the principles of paleoliquefaction studies was the first of such analyses in the country. In areas with low to moderate seismicity, geotechnical engineers often neglect and overlook liquefaction hazard, however, when it is addressed, the hazard is often overestimated due to improper characterization of the seismic loading and site characterization. To explore this observation more deeply, probabilistic seismic and liquefaction hazard assessment were carried out at the two liquefied sites and it was found that this conclusion is also valid for Hungary, but the degree of conservatism of the pseudo-probabilistic procedures decreases with increasing earthquake return period (lower annual probability of occurrence).

Dynamic rockfall risk analysis

Rockfall is a dangerous hazard on steep and susceptible slope. However, it is not easy to identify potential rockfalls on cliff mountains. Traditionally, rockfall risk analysis ignores the temporal evolution of risk due to the changes of the elements at risk, or changes in the annual probability. This may lead to an underestimation of risk in time. In this paper, we present an innovative approach for a dynamic risk analysis, and we demonstrate this approach for the ShenXianjJu scenic area case study, where rockfall represent a threat for thousands of tourists each year. Moreover, we studied the role of rock mass quality in controlling the rockfall potential and rockfall volume, since this may lead to significant changes of rockfall risk in space. We describe the use of Unmanned Aerial Vehicle, Terrestrial LiDAR and detailed field surveys to identify 34 potential rockfalls on slopes where historical rockfalls have occurred. Within ignimbrite and rhyolite rock masses rockfall blocks range in size between large and very large. Andesite derived rockfalls are characterized by medium-size to large block size. Faulted and fractured ignimbrite and rhyolite rock masses within the fault damage zone exhibit small-very small rockfall block sizes. Based on the identified potential rockfalls in the study area, we quantified the dynamic risk by considering the temporal–spatial changes of tourist activity. To demonstrate the methodology, two potential rockfalls on two heavily-used tourist routes were selected. For these scenarios we quantified the annual probability of occurrence, the reach probability, the dynamic temporal-spatial probability, and the vulnerability of tourists. The dynamic temporal probability was also calculated considering different visiting periods (e.g., working days, weekends, holidays), showing significant changes in the risk level among the different visiting periods and with time. Some of the investigated scenarios were within the ALARP zone in the first years (i.e. PLL on workday in 2017–2019), and subsequently became unacceptable (i.e. PLL on workday in 2020). As a conclusion, the research demonstrates that the traditional static risk analysis would lead to a significant rockfall risk underestimation.

North Atlantic Hurricane Winds in Warmer than Normal Seas

Tropical cyclones devastate coastlines around the world. The United States and surrounding areas experienced catastrophic extreme events in recent hurricane seasons. Understanding extreme hurricanes and how they change in a warming ocean environment is of the utmost importance. This study makes use of the historical, positive relationship between average summer sea surface temperatures (SSTs) and maximum hurricane wind speeds across the North Atlantic Basin from 1854–2018. Geographically weighted regression shows how the relationship between hurricane winds and SSTs varies across space. Each localized slope is used to increase historical wind speeds to represent winds in a three-degree Celsius warmer-than-average sea surface. The winds are then used to estimate the maximum intensity of the thirty-year hurricane (one with a 3.3% annual probability of occurrence) across the hexagonal grid using extreme value statistics. Viewing the results spatially allows for geographic patterns to emerge in the overall risk of major hurricane occurrence in warm SST environments. This study showcases the difference in the historical extreme compared to the potential future extreme in the hopes to better inform those charged with making important, life-saving decisions along the U.S. and neighboring coasts.

Risk-Based Seismic Performance Assessment of Pressurized Piping Systems Considering Ratcheting

Abstract A procedure is described for risk-based seismic performance assessment of pressurized piping systems considering ratcheting. The procedure is demonstrated on a carbon steel piping system considered for OECD-NEA benchmark exercise on quantification of seismic margins. Initially, fragility analysis of the piping system is carried out by considering variability in damping and frequency. Variation in damping is obtained from the statistical analysis of the damping values observed in earlier experiments on piping systems and components. The variation in ground motion is considered by using 20 strong motion records of the intraplate region. Floor motion of a typical reactor building of a nuclear power plant under these actual earthquake records is evaluated and applied to the piping system. The performance evaluation of the piping system in terms of ratcheting is carried out using a numerical approach, which was earlier validated with shake table ratcheting tests on piping components and systems. Three limit states representing performance levels of the piping system under seismic load are considered for fragility evaluation. For each limit state, probability of exceedance at different levels of floor motion is evaluated to generate a fragility curve. Subsequently, the fragility curves of the piping systems are convoluted with hazardous curves for a typical site to obtain the risk in terms of annual probability of occurrence of the performance limits.

Optimal Seismic Upgrade Timing in Seaports with Increasing Throughput Demand via Real Options

A real options (RO) formulation is proposed for decision-making on the timing to upgrade the seismic performance of existing seaports with increasing throughput demand in earthquake prone areas. The pay-off of the seismic upgrade investment option is estimated based on projected net earnings, repair cost, and downtime for a damaging reference seismic event having a pre-specified annual probability of occurrence. These projections inform a discrete-time RO binomial tree, following the American option valuation framework, which propagates the probability of the reference seismic event assuming Poisson temporal distribution of earthquake occurrence. The net present value of the expected annual payoff of the considered investment is used as an index supporting risk-informed decision-making discounted by the weighted average cost of capital (WACC). Numerical examples pertaining to decision makers with different capital cost, namely port authorities and terminal operators, operating in different economic environments typical of developed and developing countries are furnished to illustrate the applicability of the proposed RO formulation. It is found that high WACC and/or low throughput growth bring the optimal seismic upgrade timing forward, while earthquake consequences and upgrade cost have almost no influence on this timing.

Feasibility study of wave energy harvesting along the southern coast and islands of Iran

Due to the distance of remote coastal areas and multiple islands in the south of Iran from the national grid, establishing wave power plants is highly beneficial. Therefore, in this study, the wave energy potential at these regions is investigated. For this purpose, wave characteristics are provided using European Centre for Medium-Range Weather Forecasts (ECMWF) for ten years, and validated against buoy measurements in two different intervals. The annual, seasonal and monthly variations of wave characteristics and seasonal wave energy flux roses along with the annual occurrence probability of different sea states are also assessed. According to the results, the wave energy in the Oman Sea reaches to its maximum, 17 kW/m at Chabahar port, in summer, and the maximum wave energy in Persian Gulf and Strait of Hormuz, which reaches to 10 kW/m in Kish Island, occurs in winter. In fact, wave parameters in the central regions of Persian Gulf have the higher values than Oman Sea in this season. Finally, Chabahar port in Oman Sea, Kangan port, Kish Island and Kharg Island in the Persian Gulf are considered as the wave energy hotspots, and the most suitable wave energy converter (WEC) systems are suggested for the selected hotspots.

Risk Assessment of Shallow Landslides for Infrastructure Projects: Analysis of the Case of a Landslide in the El Cabuyal Zone

In this paper an assessment of the hazard, the vulnerability and the risk associated with shallow landslides in a watershed of the Valle de Aburra is carried out. The TRIGRS model with a Monte Carlo simulation to estimate the probability of failure in the watershed using water table depth as the trigger factor is implemented, which allows the assessment of the hazard along with its annual probability of occurrence. Additionally, a quantitative model for physical vulnerability of structures which takes into account landslide intensity and resistance of exposed elements is used. The annual risk is estimated for a house of the study site as the product of the hazard and the damage costs due to the occurrence of the catastrophic event, which considers vulnerability. The methodology used focuses on the shallow landslide occurred on October 26, 2016 on a slope within the study site, which affected the house that is being analyzed.

The use of historical information for regional frequency analysis of extreme skew surge

Abstract. The design of effective coastal protections requires an adequate estimation of the annual occurrence probability of rare events associated with a return period up to 103 years. Regional frequency analysis (RFA) has been proven to be an applicable way to estimate extreme events by sorting regional data into large and spatially distributed datasets. Nowadays, historical data are available to provide new insight on past event estimation. The utilisation of historical information would increase the precision and the reliability of regional extreme's quantile estimation. However, historical data are from significant extreme events that are not recorded by tide gauge. They usually look like isolated data and they are different from continuous data from systematic measurements of tide gauges. This makes the definition of the duration of our observations period complicated. However, the duration of the observation period is crucial for the frequency estimation of extreme occurrences. For this reason, we introduced here the concept of “credible duration”. The proposed RFA method (hereinafter referenced as FAB, from the name of the authors) allows the use of historical data together with systematic data, which is a result of the use of the credible duration concept.

Generating Random Earthquake Events for Probabilistic Tsunami Hazard Assessment

To perform probabilistic tsunami hazard assessment for subduction zone earthquakes, it is necessary to start with a catalog of possible future events along with the annual probability of occurrence, or a probability distribution of such events that can be easily sampled. For near-field events, the distribution of slip on the fault can have a significant effect on the resulting tsunami. We present an approach to defining a probability distribution based on subdividing the fault geometry into many subfaults and prescribing a desired covariance matrix relating slip on one subfault to slip on any other subfault. The eigenvalues and eigenvectors of this matrix are then used to define a Karhunen-Loeve expansion for random slip patterns. This is similar to a spectral representation of random slip based on Fourier series but conforms to a general fault geometry. We show that only a few terms in this series are needed to represent the features of the slip distribution that are most important in tsunami generation, first with a simple one-dimensional example where slip varies only in the down-dip direction and then on a portion of the Cascadia Subduction Zone.

Risk assessment and economic appraisal of protection methods for the Tarascon-Arles railway embankment

The coordination of flood management practices and the reduction of flood risk as proposed under the Plan Rhone project has led to a vast program of flood defence modernization and construction in the lower Rhone valley. One key element of the project involves the construction of a new 9km levee structure parallel to an existing railway line between the towns of Tarascon and Arles (Bouches-du-Rhone, France ) on the left bank of the Rhone, which has historically been an obstacle to the propagation of flood flows. The new levee is designed to protect the towns of Arles and Tarascon up to the 10−2 annual probability flood event, after which floodwater will flow over a 5km spillway which will be integrated into the structure. In case of overtopping of the spillway via a spillway structure, floodwater is collected in the space between the two embankments and will subsequently flow towards one of ten newly constructed flood discharge structures, spaced at regular intervals in the railway embankment. The levee will form part of a global system of defence which is designed against flooding on the Rhone with an annual probability of occurrence of 10−3 . In the event of overtopping of the levee, the railway embankment will be subjected to hydraulic loading and is at risk of damage from flood flows. During the detailed design phase of the project, options were explored for optimizing the permanent protection for the railway embankment. Using results from 2D and 3D hydraulic numerical modelling, a detailed risk assessment of the railway embankment was undertaken to evaluate its vulnerability under different hydraulic loading conditions and for different failure mechanisms using various parameters including water depth, hydraulic load, the duration of flood exposure and flow velocity. A comprehensive understanding of the main mechanisms of embankment damage under hydraulic loading (internal/ external erosion, overtopping, rotational failure etc.), existing geotechnical conditions and the railway embankment structure were required to undertake the risk assessment. For each hydraulic loading scenario, a detailed economic appraisal was undertaken for each method of protection involving the evaluation of damages associated with disruption to train services and the associated costs to repair the structure. The final stage of the project involved integrating the economic assessment into a wider reaching multi-criteria analysis including indicators for train security, maintainability and environmental impact aspects. The multi-criteria approach was tested under two management strategies to evaluate the effectiveness of each embankment protection system. This paper outlines how the risk assessment, economic appraisal and management-strategy based multi-criteria approach resulted in a highly optimized system of embankment protection with significant gains in terms of both reduced cost of implementation and environmental enhancement whilst maintaining the high levels of railway security required by SNCF-RESEAU.

Production induced subsidence and seismicity in the Groningen gas field – can it be managed?

Production induced subsidence and seismicity in the Groningen gas field – can it be managed?

GEAR1: A Global Earthquake Activity Rate Model Constructed from Geodetic Strain Rates and Smoothed Seismicity

Global earthquake activity rate model 1 (GEAR1) estimates the rate of shallow earthquakes with magnitudes 6–9 everywhere on Earth. It was designed to be reproducible and testable. Our preferred hybrid forecast is a log–linear blend of two parent forecasts based on the Global Centroid Moment Tensor (CMT) catalog (smoothing 4602 m ≥5.767 shallow earthquakes, 1977–2004) and the Global Strain Rate Map version 2.1 (smoothing 22,415 Global Positioning System velocities), optimized to best forecast the 2005–2012 Global CMT catalog. Strain rate is a proxy for fault stress accumulation, and earthquakes indicate stress release, so a multiplicative blend is desirable, capturing the strengths of both approaches. This preferred hybrid forecast outperforms its seismicity and strain‐rate parents; the chance that this improvement stems from random seismicity fluctuations is less than 1%. The preferred hybrid is also tested against the independent parts of the International Seismological Centre‐Global Earthquake Model catalog ( m ≥6.8 during 1918–1976) with similar success. GEAR1 is an update of this preferred hybrid. Comparing GEAR1 to the Uniform California Earthquake Rupture Forecast Version 3 (UCERF3), net earthquake rates agree within 4% at m ≥5.8 and at m ≥7.0. The spatial distribution of UCERF3 epicentroids most resembles GEAR1 after UCERF3 is smoothed with a 30 km kernel. Because UCERF3 has been constructed to derive useful information from fault geometry, slip rates, paleoseismic data, and enhanced seismic catalogs (not used in our model), this is encouraging. To build parametric catastrophe bonds from GEAR1, one could calculate the magnitude for which there is a 1% (or any) annual probability of occurrence in local regions. Online Material: Discussion of forecast‐scoring metrics, tables of scoring results, and source code and data files needed to reproduce forecast.

Cluster Analysis of the Wind Events and Seasonal Wind Circulation Patterns in the Mexico City Region

The residents of Mexico City face serious problems of air pollution. Identifying the most representative scenarios for the transport and dispersion of air pollutants requires the knowledge of the main wind circulation patterns. In this paper, a simple method to recognize and characterize the wind circulation patterns in a given region is proposed and applied to the Mexico City winds (2001–2006). This method uses a lattice wind approach to model the local wind events at the meso-β scale, and hierarchical cluster analysis to recognize their agglomerations in their phase space. Data of the meteorological network of Mexico City was used as input for the lattice wind model. The Ward’s clustering algorithm with Euclidean distance was applied to organize the model wind events in seasonal clusters for each year of the period. Comparison of the hourly population trends of these clusters permitted the recognition and detailed description of seven circulation patterns. These patterns resemble the qualitative descriptions of the Mexico City wind circulation modes reported by other authors. Our method, however, permitted also their quantitative characterization in terms of the wind attributes of velocity, divergence and vorticity, and an estimation of their seasonal and annual occurrence probabilities, which never before were quantified.