Findings from University College in the Area of Earth Science Described (Evaluating simplified methods for liquefaction assessment for loss…

Findings from University College in the Area of Earth Science Described (Evaluating simplified methods for liquefaction assessment for loss estimation)

By a News Reporter-Staff News Editor at Science Letter -- Research findings on Science - Earth Science are discussed in a new report. According to news reporting originating from London, United Kingdom, by NewsRx correspondents, research stated, "Currently, some catastrophe models used by the insurance industry account for liquefaction by applying a simple factor to shaking-induced losses. The factor is based only on local liquefaction susceptibility and this highlights the need for a more sophisticated approach to incorporating the effects of liquefaction in loss models."

Our news editors obtained a quote from the research from University College, "This study compares 11 unique models, each based on one of three principal simplified liquefaction assessment methods: liquefaction potential index (LPI) calculated from shear-wave velocity, the HAZUS software method and a method created specifically to make use of USGS remote sensing data. Data from the September 2010 Darfield and February 2011 Christchurch earthquakes in New Zealand are used to compare observed liquefaction occurrences to forecasts from these models using binary classification performance measures. The analysis shows that the best-performing model is the LPI calculated using known shear-wave velocity profiles, which correctly forecasts 78% of sites where liquefaction occurred and 80% of sites where liquefaction did not occur, when the threshold is set at 7. However, these data may not always be available to insurers. The next best model is also based on LPI but uses shear-wave velocity profiles simulated from the combination of USGS V-S30 data and empirical functions that relate V-S30 to average shear-wave velocities at shallower depths. This model correctly forecasts 58% of sites where liquefaction occurred and 84% of sites where liquefaction did not occur, when the threshold is set at 4. These scores increase to 78 and 86 %, respectively, when forecasts are based on liquefaction probabilities that are empirically related to the same values of LPI. This model is potentially more useful for insurance since the input data are publicly available. HAZUS models, which are commonly used in studies where no local model is available, perform poorly and incorrectly forecast 87% of sites where liquefaction occurred, even at optimal thresholds. This paper also considers two models (HAZUS and EPOLLS) for estimation of the scale of liquefaction in terms of permanent ground deformation but finds that both models perform poorly, with correlations between observations and forecasts lower than 0.4 in all cases."

According to the news editors, the research concluded: "Therefore these models potentially provide negligible additional value to loss estimation analysis outside of the regions for which they have been developed."

For more information on this research see: Evaluating simplified methods for liquefaction assessment for loss estimation. Natural Hazards and Earth System Sciences, 2017;17(5):781-800. Natural Hazards and Earth System Sciences can be contacted at: Copernicus Gesellschaft Mbh, Bahnhofsallee 1E, Gottingen, 37081, Germany. (Copernicus Publications - www.copernicus.org; Natural Hazards and Earth System Sciences - publications.copernicus.org)

The news editors report that additional information may be obtained by contacting I. Kongar, UCL, Dept. of Civil Environm & Geomat Engn, Earthquake & People Interact Center, London WC1E 6BT, United Kingdom. Additional authors for this research include T. Rossetto and S. Giovinazzi (see also Science - Earth Science).

Keywords for this news article include: London, United Kingdom, Europe, Earth Science, Science, University College.

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