Workflows for Construction of Spatio-Temporal Probabilistic Maps for Volcanic Hazard Assessment

Probabilistic hazard assessments for studying overland pyroclastic flows or atmospheric ash clouds under short timelines of an evolving crisis, require using the best science available unhampered by complicated and slow manual workflows. Although deterministic mathematical models are available, in most cases, parameters and initial conditions for the equations are usually only known within a prescribed range of uncertainty. For the construction of probabilistic hazard assessments, accurate outputs and propagation of the inherent input uncertainty to quantities of interest are needed to estimate necessary probabilities based on numerous runs of the underlying deterministic model. Characterizing the uncertainty in system states due to parametric and input uncertainty, simultaneously, requires using ensemble based methods to explore the full parameter and input spaces. Complex tasks, such as running thousands of instances of a deterministic model with parameter and input uncertainty require a High Performance Computing infrastructure and skilled personnel that may not be readily available to the policy makers responsible for making informed risk mitigation decisions. For efficiency, programming tasks required for executing ensemble simulations need to run in parallel, leading to twin computational challenges of managing large amounts of data and performing CPU intensive processing. The resulting flow of work requires complex sequences of tasks, interactions, and exchanges of data, hence the automatic management of these workflows are essential. Here we discuss a computer infrastructure, methodology and tools which enable scientists and other members of the volcanology research community to develop workflows for construction of probabilistic hazard maps using remotely accessed computing through a web portal.

How Good is a Paleoseismic Record of Megathrust Earthquakes for Probabilistic Forecasting?

Time-dependent earthquake forecast depends on the frequency and number of past events and time since the last event. Unfortunately, only a few past events are historically documented along subduction zones where forecasting relies mostly on paleoseismic catalogs. We address the role of dating uncertainty and completeness of paleoseismic catalogs on probabilistic estimates of forthcoming earthquakes using a 3.6-ka-long catalog including 11 paleoseismic and 1 historic (Mw≥8.6) earthquakes that preceded the great 1960 Chile earthquake. We set the clock to 1940 and estimate the conditional probability of a future event using five different recurrence models. We find that the Weibull model predicts the highest forecasting probabilities of 44% and 72% in the next 50 and 100 yr, respectively. Uncertainties in earthquake chronologies due to missing events and dating uncertainties may produce changes in forecast probabilities of up to 50%. Our study provides a framework to use paleoseismic records in seismic hazard assessments including epistemic uncertainties.

Volcano monitoring and hazard assessments in Chile

Volcanism in Chile occurs in a variety of tectonic settings but mostly in the context of oceanic-continental plate collision, including 92 potentially active volcanoes. There have been more than 30 documented eruptions in the last few centuries. The Servicio Nacional de Geología y Minería (SERNAGEOMIN) is a statutory agency of the Government of Chile responsible for volcano monitoring and hazard assessments across the country. After the impacts derived from volcanic activity at the end of the 20th century, SERNAGEOMIN created the Volcano Hazards Program and the Observatorio Volcanológico de Los Andes del Sur (OVDAS). Despite this effort, most volcanoes in Chile remained unmonitored. In 2008, the aftermath of the eruption of Chaitén led to a nationwide program in order to improve eruption forecasting, development of early warning capabilities and our state of readiness for volcanic impacts through hazard assessments. In the last decade responses to volcanic crises have been indubitably successful providing technical advice before and during volcanic eruptions. El volcanismo en Chile ocurre en una amplia variedad de regímenes tectónicos, aunque principalmente en el contexto de la colisión de placas. Alrededor de 92 volcanes son considerados potencialmente activos y más de 30 presentan actividad histórica documentada en los últimos siglos. El Servicio Nacional de Geología y Minería (SERNAGEOMIN) es la agencia gubernamental responsable de la evaluación de peligros y monitoreo de la actividad volcánica en el país. Como consecuencia de los impactos derivados de las erupciones volcánicas ocurridas hacia finales del siglo pasado, SERNAGEOMIN creó el Programa de Riesgo Volcánico y el Observatorio Volcanológico de los Andes del Sur (OVDAS). No obstante, a pesar de este esfuerzo la mayoría de los volcanes en Chile se mantenían sin monitoreo. Luego de los impactos derivados de la erupción del volcán Chaitén en 2008, un nuevo programa nacional fue creado con el fin de fortalecer la vigilancia y la evaluación de los peligros volcánicos en el país. En la última década, la respuesta a crisis volcánicas ha sido exitosa, proporcionando apoyo técnico en forma previa y durante erupciones.

Macroseismic intensity attenuation equations for Central Asia earthquakes

Based on macroseismic survey data for strong earthquakes in Central Asia, the coefficients of attenuation of seismic intensities with distance in the Blake-Shebalin- and Kovesligethy -type equations were refined. A new generalized dependence of macroseismic intensity attenuation on distance, taking into account the depth of the earthquake hypocentre, were obtained. Relations between the minor and major axes of the ellipse approximating real isoseists depending on the shaking strength, source depth and earthquake magnitude were found. With the example of the territory of eastern Uzbekistan, the influence of the choice of the law of seismic intensity attenuation with distance on the obtained seismic hazard assessments is investigated.

The codification of hazard and its impact on the hazard versus risk controversy

The long running controversy about the relative merits of hazard-based versus risk-based approaches has been investigated. There are three levels of hazard codification: level 1 divides chemicals into dichotomous bands of hazardous and non-hazardous; level 2 divides chemicals into bands of hazard based on severity and/or potency; and level 3 places each chemical on a continuum of hazard based on severity and/or potency. Any system which imposes compartments onto a continuum will give rise to issues at the boundaries, especially with only two compartments. Level 1 schemes are only justifiable if there is no variation in severity, or potency or if there is no threshold. This is the assumption implicit in GHS/EU classification for carcinogenicity, reproductive toxicity and mutagenicity. However, this assumption has been challenged. Codification level 2 hazard assessments offer a range of choices and reduce the built-in conflict inherent in the level 1 process. Level 3 assessments allow a full range of choices between the extremes and reduce the built-in conflict even more. The underlying reason for the controversy between hazard and risk is the use of level 1 hazard codification schemes in situations where there are ranges of severity and potency which require the use of level 2 or level 3 hazard codification. There is not a major difference between level 2 and level 3 codification, and they can both be used to select appropriate risk management options. Existing level 1 codification schemes should be reviewed and developed into level 2 schemes where appropriate.