Macroseismic Intensity Assessment Method for Online Questionnaires in New Zealand

Abstract eng:
The Canterbury (New Zealand) earthquake sequence of 2010-2012 caused unexpectedly high levels of damage, and was unparalleled in terms of the quantum of disruption and losses for New Zealand. GeoNet (New Zealand’s national geological hazards monitoring service, http://www.geonet.org.nz/) received more than 11,000 online questionnaires from the two most significant earthquakes in the sequence; the main shock (Mw 7.1) and its damaging aftershock (Mw 6.2), challenging the online facility. In addition, four recent moderate sized events (Cook Strait, 21 July 2013, ML 6.5; Lake Grassmere, 16 August 2013, Mw 6.6; Eketahuna, 20 January 2014, ML 6.2; Christchurch, 14 February 2016, Mw 5.7) have confirmed the immense public interest in filling in online questionnaires. Although GeoNet automatically calculates Modified Mercalli Intensity (MMI) values for each report, there is currently no method to convert this data into a reliable spatial damage distribution at a community scale. This limits our ability to understand past disasters and help future evacuation and emergency planning. The large number of responses has enabled us to develop a method to calculate community MMI values from the invididual felt reports, based on work carried out overseas and adapted to New Zealand data and macroseismic scale. This paper presents the development of the method, its application to eight recent New Zealand earthquakes and calibration methods currently under progress.

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