Classification of long-term very long period (VLP) volcanic earthquakes at Whakaari/White Island volcano, New Zealand

Iseul Park,Arthur Jolly,Ben Kennedy,Ivan Lokmer

doi:10.1186/s40623-020-01224-z

Iseul Park, Arthur Jolly + Show 2 more

Open Access

https://doi.org/10.1186/s40623-020-01224-z

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Abstract

We have observed very long period earthquakes (VLPs) over the period 2007 to the end of 2019 at Whakaari/White Island volcano, New Zealand. The earthquakes exhibit similitude between waveforms which suggests repeating source locations and processes. VLPs recorded at two permanent stations were detected using waveform semblance and were then classified into two main families (F1 and F2) using a clustering analysis. The two families are characterized by ‘mirror image’ reverse waveform polarity suggesting that they are genetically related, but occur during different evolutionary phases of volcanic activity. F1 events occurred throughout the observation period, while F2 events mainly occurred as swarms that mark the onset of volcanic unrest. A detailed cluster analysis reveals possible sub-families implying slight temporal evolutions within a family. Our results add to our understanding of the volcanic magma–hydrothermal system at Whakaari/White Island indicating that relatively stable VLP sources may be exploited to improve monitoring for future unrest.

Highlights

Whakaari/White Island (Fig. 1a) is one of New Zealand’s most active volcanoes and has been a frequent tourist destination
We find that very long period earthquakes (VLPs) source excitations are pervasive during periods of both unrest and repose, but that VLP families relate to different periods of quiescence and unrest/eruption
This study provides the first attempt of the comprehensive detection and analysis of long-term VLP earthquakes at Whakaari/White Island

Summary

Introduction

Whakaari/White Island (Fig. 1a) is one of New Zealand’s most active volcanoes and has been a frequent tourist destination. Caudron et al (2018) studied two VLP events recorded during the 2013 eruption episode and found a similar source depth to the 2011 swarm (Jolly et al 2017). VLP signals within each family display similar waveforms event-to-event (Fig. 2c) which may indicate a stable source process (e.g., Chouet 1996; Stephens and Chouet 2001; Green and Neuberg 2006; Petersen et al 2006; Park et al 2019), despite the variation in surface activity (Edwards et al 2017).

Results

Conclusion