Contemporary ground deformation in the Taupo Rift and Okataina Volcanic Centre from 1998 to 2011, measured using GPS

Holden, Lucas; Wallace, Laura; Beavan, John; Fournier, N.; Fernand, Raymond Alexander; Aillères, Laurent; Silcock, D.

doi:10.1093/gji/ggv243

Cited by 22 publications

(10 citation statements)

References 64 publications

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“…Villamor & Berryman 2001). Holden et al (2015) also observe such a contractional signal from their independent processing of data from the Okataina region. This contraction coincides with a large region of rapid subsidence (up to 2 cm a -1 ) observed from interferometric synthetic aperture radar (InSAR) data, which Hamling et al (2015) suggest is due to cooling of a magma body beneath the TVZ.…”

Section: Discussionmentioning

confidence: 84%

“…It is likely that the observed GPS contraction is also related to magmatic cooling processes, and that it is masking tectonic deformation within the central TVZ (e.g. Holden et al 2015).…”

Section: Discussionmentioning

confidence: 99%

“…These data have been used in numerous papers to define the overall kinematics and rates of crustal deformation throughout the New Zealand plate boundary zone (e.g. Darby & Meertens 1995;Bourne et al 1998;Beavan et al 1999Beavan et al , 2007Beavan et al , 2010Beavan et al , 2011aBeavan et al , 2011bBeavan et al , 2012Darby et al 2000;Beavan & Haines 2001;Darby & Beavan 2001;Moore et al 2002;Nicol & Beavan 2003;Wallace et al 2004Wallace et al , 2007Wallace et al , 2012aEllis et al 2006aEllis et al , 2006bNicol & Wallace 2007;Holden et al 2015; among many others).…”

Section: The New Zealand Campaign Gps Datasetmentioning

confidence: 99%

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New Zealand GPS velocity field: 1995–2013

Beavan

Wallace

Palmer

et al. 2016

New Zealand Journal of Geology and Geophysics

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We collate nearly two decades of campaign GPS data gathered at over 900 sites throughout New Zealand to release a New Zealand nationwide GPS velocity field. The data span the entire North and South islands of New Zealand with a typical spacing of 10-20 km and a denser network (c. 2-8 km spacing) in the Wellington region, central Taupo Volcanic Zone and parts of the Arthur's Pass area. The dataset provides the most comprehensive-to-date view of crustal deformation within the Australia-Pacific plate boundary zone in the New Zealand region. We discuss the data acquisition, processing and derivation of the velocities and uncertainties. We also undertake corrections for earthquake displacements to obtain a velocity field that is largely representative of interseismic deformation between 1995 and 2013.

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Section: Discussionmentioning

confidence: 84%

“…It is likely that the observed GPS contraction is also related to magmatic cooling processes, and that it is masking tectonic deformation within the central TVZ (e.g. Holden et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Section: The New Zealand Campaign Gps Datasetmentioning

confidence: 99%

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New Zealand GPS velocity field: 1995–2013

Beavan

Wallace

Palmer

et al. 2016

New Zealand Journal of Geology and Geophysics

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“…However, while dyke-accommodated rifting has been directly observed in other continental rifts (Kendall et al, 2005;Ebinger et al, 2013) and realistically has to have occurred during the 1886 eruption, it has not yet been detected in the TVZ in the modern instrumental era. Analysis of GPS data from the OVC area found that strain in the region surrounding the Tarawera fissure should promote the intrusion of dykes (Holden et al, 2015). Other geodetic studies, however, found that the OVC and TVZ are more accurately described as contractional areas at present (Hamling et al, 2015;Dimitrova et al, 2016;Haines and Wallace, 2020).…”

Section: Geological Backgroundmentioning

confidence: 95%

Earthquake Analysis Suggests Dyke Intrusion in 2019 Near Tarawera Volcano, New Zealand

et al. 2021

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Tarawera volcano (New Zealand) is volumetrically dominated by rhyolitic lavas and pyroclastic deposits, but the most recent event in AD 1886 was a basaltic Plinian fissure eruption. In March 2019 a swarm of at least 64 earthquakes occurred to the NE of Tarawera volcano, as recorded by the New Zealand Geohazard Monitoring Network (GeoNet). We use seismological analysis to show that this swarm was most likely caused by a dyke that intruded into the brittle crust between depths of 8–10 km and propagated toward Tarawera volcano for 2 km at a rate of 0.3–0.6 m s−1. We infer that this was a dyke of basaltic composition that was stress-guided toward Tarawera volcano by the topographic load of the volcanic edifice. Dyke intrusions of this nature are most likely a common occurrence but a similar process may have occurred during the 1886 eruption with a dyke sourced from some lateral distance away from the volcano. The 2019 intrusion was not detected by InSAR geodesy and we use synthetic models to show that geodetic monitoring could only detect a ≥6 m wide dyke at these depths. Improvements to geodetic monitoring, combined with detailed seismological analysis, could better detect future magmatic intrusions in the region and serve to help assess ongoing changes in the magmatic system and the associated possibilities of a volcanic event.

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“…These studies (e.g. Seebeck et al 2010Seebeck et al , 2014de Ronde et al 2016b;Heise et al 2016;Caratori Tontini et al 2016;Holden et al 2015Holden et al , 2017Benson et al 2021;Hamling et al 2022), which provide a snapshot of the present-day state of Ōkataina, can be combined with geochemical and physical volcanological data from past events to build a full picture of Ōkataina in the present day, including the likely locations of magma bodies, structural features controlling vent locations, and other features. An overview of current geophysical work and how it relates to the Ōkataina story is thus included in the final chapter of this thesis.…”

Section: ōKataina In the Present Daymentioning

confidence: 99%

Geochemistry, Magmatic Processes and Timescales of Recent Rhyolitic Eruptives of the Ōkataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa/New Zealand

Elms¹

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This thesis investigates the magmatic processes that operated at Ōkataina volcanic centre prior to and during the rhyolitic events of its most recent eruption sequence, the Rotorua Subgroup (erupted since 25.4 ka), with a specific focus on timescales of human interest. Further context is derived with data from the 52.8 ka Rotoiti (caldera-forming) and Earthquake Flat eruptions, and selected Mangaone Subgroup events that occurred between the 52.8 and 25.4 ka. The regular occurrence of these events provides regular snapshots of the magmatic system over this time period. Whole-rock, glass, and mineral compositional data and timescales modelled from diffusion gradients are compared within geographical and physical volcanological contexts. These data provide a picture of the recent evolution of Ōkataina, shedding light on how quickly the volcano could awaken from its current dormancy to produce a new rhyolitic event, and what that event might be like. Geochemical data from Mangaone Subgroup eruptives show that the post-caldera magmatic system recovered over c. 27 kyr, with increasingly evolved and radiogenic compositions erupted during these events. The post-25.4 ka Rotorua Subgroup shows a more steady evolution, trending towards less radiogenic products towards the present day. Modern Ōkataina comprises three vent clusters, the intra-caldera Mt. Tarawera (formed by the 21.9 ka Ōkareka, 17.5 ka Rerewhakaaitu, 14 ka Waiohau and 1314 AD Kaharoa eruptive episodes) and Haroharo Massif (the 25.2 ka Te Rere, 9.4 ka Rotomā, 7.9 ka Mamaku and 5.5 ka Whakatāne), and the Ōkareka Embayment (the 25.2 ka Te Rere, 15.6 ka Rotorua) on the western edge of the caldera. Most eruptions were geochemically complex, with multiple magmas, some of which were repeated between eruptions. Variations in whole-rock and glass geochemistry are controlled by both the dominant mineral assemblage and external inputs, and relate to the geographical region and timing of when each magma erupted. Each vent region shows evidence for distinct features in its shallower magmatism (i.e. that producing the final-erupted magma compositions), super-imposed on temporal trends controlled by the deeper system. This deeper system beneath Haroharo and Tarawera appears to be more unitary or inter-connected. However, the Ōkareka Embayment is unique in that it appears to involve multiple magmatic systems. Back-scattered electron imaging of orthopyroxenes from the Rotorua, Waiohau and Whakatāne eruptives (and selected plagioclase from the Rotorua), coupled with major-element analyses of the orthopyroxenes, imply that open-system processes are common at Ōkataina, at least in the early stages of eruptible magma body assembly. These processes are reflected in diverse core compositions and complex zonation patterns, narrowing to more uniform rims that are in equilibrium with the compositions of the host melts. Not all cores are in equilibrium with the associated whole-rock compositions, but are in equilibrium with whole-rock compositions from other magmas erupted nearby, further demonstrating open-system crystal exchange and the repeated tapping of some magma sources from one event to another. Melt segregation and magma body assembly takes place over decades up to a century or two, with magma residence times on the order of centuries to millennia, or (if prematurely triggered) as short as months. Priming or triggering events such as heating by basaltic injection (common in the Ōkataina rhyolite eruptions) occur over decades prior to eruption. Quartz-hosted, sealed melt inclusions preserve volatile contents of c. 3-6 wt% H2O and c. 15-125 ppm CO2, with values tending to decrease in younger eruptions, although Waiohau samples have relatively low H2O, and the Rotorua samples have relatively low CO2. Overall, the Ōkataina eruptives have remarkably low CO2 contents compared with international datasets. There are weak correlations between H2O and CO2 contents coexisting in magmas within individual vent regions, but little system-wide coherence due to each region having differing trends (a step-wise drop at Tarawera versus a steady decrease in the young Haroharo eruptions). Scatter in data from sealed melt inclusions, and relatively lower H2O contents in open-ended inclusions (embayments) indicate pre-eruptive volatile losses, driven by crystallisation and/or open-system degassing. The H2O contents of the inner parts of embayments suggest an initial slow decompression at the start of the final magma ascent may also play a minor role. Magma ascent rates are low to moderate (0.1-4.4 m.s-1), with the Ōkareka Embayment eruptives having notably faster ascent rates than those from Tarawera or Haroharo. Both the sealed melt inclusion volatile contents and derived magma ascent rates are similar to those observed or inferred from other silicic eruptions worldwide and are notably comparable to those of super-eruptions, indicating that magma volume and overpressure do not influence ascent rate at eruption onset. Current geophysical observations suggest that a viable magma source currently exists under the southwestern end of Haroharo, and that basaltic diking activity is ongoing in the Ōkataina area. While basaltic eruptions can occur with little warning (e.g. Tarawera, 1886 CE), it is more likely that a future Ōkataina event will be prolonged and rhyolitic. The volcano can rejuvenate into an eruption-ready state within human lifetimes (i.e. decades), and final pre-eruptive warnings from geophysical monitoring could be as short as only a few hours. A new rhyolitic episode could have major impacts, lasting several years and involving both voluminous lavas and widespread fall deposition.

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Contemporary ground deformation in the Taupo Rift and Okataina Volcanic Centre from 1998 to 2011, measured using GPS

Cited by 22 publications

References 64 publications

New Zealand GPS velocity field: 1995–2013

New Zealand GPS velocity field: 1995–2013

Earthquake Analysis Suggests Dyke Intrusion in 2019 Near Tarawera Volcano, New Zealand

Geochemistry, Magmatic Processes and Timescales of Recent Rhyolitic Eruptives of the Ōkataina Volcanic Centre, Taupō Volcanic Zone, Aotearoa/New Zealand

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