Insights into fluid transport mechanisms at White Island from analysis of coupled very long-period (VLP), long-period (LP) and high-frequency (HF) earthquakes

Abstract

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Relating gas ascent to eruption triggering for the April 27, 2016, White Island (Whakaari), New Zealand eruption sequence

“…The synthetic waveforms are computed at a position 1 km below sea level. The recovered solution is within 200 m of the true source position and is similar to locations derived from 12 stations available in 2011 (see Jolly et al 2017). The synthetic location is determined using the same method as outlined in the methods section observed just prior to the pulse 4 eruption (Figs.…”

“…The free surface was then altered combining a Digital Elevation Model (DEM) and a bathymetry model of the surrounding seabed (Prasetya and Wang 2011), in order to reflect the topography of the volcanic edifice (for further details see Jolly et al 2017). The source location obtained in the previous section was used for the computations.…”

“…The first pre-eruption VLP occurs approximately 2 h prior to the first eruption. Given the source depth of 800-1000 m, the VLP may not be related to the advective transfer of gas from the inferred magma supply zone (e.g., Christenson et al 2017;Jolly et al 2017) into the quasi-stable shallow hydrothermal system (Caudron et al Fig. 9 Normalized time-dependent seismic moment.…”

Geophysical examination of the 27 April 2016 Whakaari/White Island, New Zealand, eruption and its implications for vent physiognomies and eruptive dynamics

“…The existence of water has given Whakaari many periods of continuous hydrothermal activity, with sporadic phreatic eruptions as well as phreatomagmatic and Strombolian eruptions (Nishi et al 1996;Cole et al 2000;Mayer et al 2015). It is inferred that these eruptions originate at shallow depths (< 1.0 km) (i.e., Nishi et al 1996;Jolly et al 2017a) due to the theorized location (0.5-2.0 km in depth) of the magma chamber in the upper crust (Houghton and Nairn 1991;Cole et al 2000;Werner et al 2008). The hydrothermal activity sourced from these shallow depths is expressed on the surface during non-eruptive periods as intense degassing fumaroles, mud bubbles, steaming ground, and hot springs (Houghton and Nairn 1991;Heap et al 2015).…”

“…However, since 2011 Geological and Nuclear Sciences (GNS) has operated a varying number of seismic stations, which has led to modern volcanic monitoring. Subsequently, ever since seismometers have been installed on the island, many have described in detail the different types of signals produced by the Whakaari volcanic system: volcano-tectonic (VT) events (Nishi et al 1996), long-period (LP) events (Sherburn and Scott 1993), very long-period (VLP) events (Jolly et al 2017a), and volcanic tremor (Sherburn et al 1991).…”