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Kaiser K.F.,Swiss Federal Institute of forest | Kaiser K.F.,University of Zürich | Friedrich M.,University of Hohenheim | Miramont C.,French National Center for Scientific Research | And 9 more authors.
Quaternary Science Reviews | Year: 2012

Here we present the entire range of Lateglacial tree-ring chronologies from Switzerland, Germany, France, covering the Lateglacial north and west of the Alps without interruption as well as finds from northern Italy, complemented by a 14C data set of the Swiss chronologies. Geographical expansion of cross-matched European Lateglacial chronologies, limits and prospects of teleconnection between remote sites and extension of the absolute tree-ring chronology are discussed. High frequency signals and long-term fluctuations are revealed by the ring-width data sets of the newly constructed Swiss Late-glacial Master Chronology (SWILM) as well as the Central European Lateglacial Master Chronology (CELM) spanning 1606 years. They agree well with the characteristics of Boelling/Alleroed (GI-1) and the transition into Younger Dryas (GS-1). The regional chronologies of Central Europe may provide improved interconnection to other terrestrial or marine high-resolution archives. Nevertheless the breakthrough to a continuous absolute chronology back to Boelling (GI-1e) has not yet been achieved. A gap remains, even though it is covered by several floating chronologies from France and Switzerland. © 2010 Elsevier Ltd.

Winson A.E.G.,Nanyang Technological University | Costa F.,Nanyang Technological University | Newhall C.G.,Nanyang Technological University | Woo G.,Risk Management Solutions RMS | Woo G.,Nanyang Technological University
Journal of Applied Volcanology | Year: 2014

Volcano Alert Levels (VALs) are used by volcanologists to quickly and simply inform local populations and government authorities of the level of volcanic unrest and eruption likelihood. Most VALs do not explicitly forecast volcanic activity but, in many instances they play an important role in informing decisions: defining exclusion zones and issuing evacuation alerts. We have performed an analysis on VALs (194 eruptions, 60 volcanoes) to assess how well they reflect unrest before eruption and what other variables might control them. We have also looked at VALs in cases where there was an increase in alert level but no eruption, these we term 'Unrest without eruption' (UwE). We have analyzed our results in the context of eruption and volcano type, instrumentation, eruption recurrence, and the population within 30 km. We found that, 19% of the VALs issued between 1990 and 2013 for events that ended with eruption accurately reflect the hazard before eruption. This increases to ~30% if we only consider eruptions with a VEI ≥ 3. VALs of eruptions from closed-vent volcanoes are more appropriately issued than those from open-vents. These two observations likely reflect the longer and stronger unrest signals associated with large eruptions from closed vents. More appropriate VAL issuance is also found in volcanoes with monitoring networks that are moderately-well equipped (3-4 seismometers, GPS and gas monitoring). There is also a better correlation between VALs and eruptions with higher population density. We see over time (1990 to 2013) that there was an increase in the proportion of 'UwE' alerts to other alerts, suggesting increasing willingness to use VALs well before an eruption is certain. The number of accurate VALs increases from 19% to 55% if we consider all UwE alerts to be appropriate. This higher 'success' rate for all alerts (with or without eruption) is improving over time, but still not optimal. We suggest that the low global accuracy of the issuance of VALs could be improved by having more monitoring networks equipped to a medium level, but also by using probabilistic hazard management during volcanic crisis. © 2014 Winson et al.

Fitzenz D.D.,Risk Management Solutions RMS | Nyst M.,Risk Management Solutions RMS
Bulletin of the Seismological Society of America | Year: 2015

We present a risk assessment perspective on earthquake recurrence on mature faults and the ways that it can be modeled. Specific needs unique to risk models compared with probabilistic seismic-hazard assessment include (1) the determination of loss per event to assess the correlation of risk between sites for portfolio management, (2) loss at all return periods, and sometimes (3) realizations of the order in which events occur. We use three mature faults in New Zealand as a case study and review the impact of parameter and model uncertainty on risk metrics. We review the physical characteristics of several faulting environments, contrasting them against the properties of three probability density functions (PDFs) widely used to characterize such interevent time distributions. We review the data available to constrain both the priors and the recurrence process and conclude that to use them to quantify the recurrence of large events on mature faults, it is best to compute a Bayesian combination of models (i.e., the weighted average of individual PDFs using their Bayes factors). Finally, we propose the following to the community: (1) the initiation of a general discussion on how best to incorporate our knowledge (e.g., from earthquake geology) on plausible models and model parameters, while preserving the information on what we do not know and (2) the creation and maintenance of a global database of priors, data, and model evidence, classified by tectonic region, fluid characteristic, fault geometry, and other relevant properties so that we can monitor whether the timedependent recurrence behavior of certain types of faults or faulting environments can be better described by one (or a combination of) recurrence model(s). © 2015, Seismological Society of America. All rights reserved.

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