Analysis of the LaMEVE database on global quaternary large magnitude explosive volcanism

A database of Quaternary large magnitude explosive eruptions (M ≥ 4) is under development as part of the VOGRIPA project on global volcanic hazards and risk. The database currently consists of 1929 entries from 481 Quaternary volcanoes. The database can be applied to constraining the magnitude-frequency relationship of global and regional volcanism. Under-recording is a major feature of the data with the proportion of events recorded from written records or geological data decreasing markedly back in time. In the Holocene the proportion of eruptions recorded by geological studies prior to 2000 years BP is assessed at about 15%. Prior to 100 ka less than 1% of eruptions have been recorded. Under-recording is more marked for smaller eruptions because preservation potential of deposits increases with eruption magnitude. Analysis of the data indicates that, notwithstanding under-recording, temporal changes in global volcanism are apparent, notably a late glacial increase in the 13 to 9 ka period. Application of extreme value statistics to a Holocene subset of data, corrected for under-recording, enables construction of a magnitude-frequency relationship for global volcanism. Return periods based on maximum likelihood statistical analysis are 7.9 years for M ≥ 4, 35 years for M ≥ 5, and 370 years for M ≥ 7.0 with uncertainty increasing with magnitude. The return periods depend on the threshold chosen between the main part of the distribution and the extreme value tail and the results cited here are for a threshold of M = 4. For the largest magnitude eruptions (M > 7.5) the Holocene period is too short to obtain a meaningful result. Data from Japan constitutes almost 50% of global data. The LaMEVE database is to be made publically available in early 2011 with a web interface allowing the input of new data and corrections by the volcanological community.