Taupō volcano (New Zealand) is distinguished as the source of Earth's youngest supereruption (∼25.5 ka), with Lake Taupō occupying the resulting caldera. Taupō has also produced eruptions of a wide variety of sizes, styles and associated landscape responses over a ∼350 kyr period. Early Taupō (>54 ka) is poorly demarcated, merging with Maroa to the north, and is represented by widely scattered, geochemically distinct, effusive domes and explosive eruption products from vents all around the modern lake. Taupō had two independent magmatic systems from 54–25.5 ka, one that led to the Oruanui event focussed beneath the area of the modern lake and a second, northeast of the lake that has remained active to the present. Following the Oruanui supereruption, the rebuilt modern hyperactive Taupō magmatic system is primarily focussed beneath the lake and has generated 25 rhyolitic eruptions since ∼12 ka. The young rhyolite magmas come from an evolving silicic magma reservoir, but vary widely in their eruptive sizes and destructive potential. In the modern era Taupō experiences unrest every decade or so, but uncertainties remain over the nature of the magma reservoir and the processes that drive unrest or eruptive activity that require new geophysical data and interpretations.
The dataset provided includes seismic anisotropy results using a 10-year catalogue around Taupō volcano (January 2010 to December 2019). For the seismic anisotropy measurements, we used seismic data from 23 stations managed by GeoNet. The earthquake catalogue for this dataset was determined by Illsley-Kemp et al. (2021) using matched-filtered earthquake detection (Chamberlain & Townend, 2018). The earthquake templates for the matched-filtered detection were obtained from the GeoNet catalogue with revised manual picks. In case you use this data, please cite the following publications: Bakkar, H. (2022). Seismic anisotropy and time-frequency analyses during Taupō's 2019 unrest [Master's thesis, Victoria University of Wellington]. Illsley-Kemp, F., Barker, S. J., Wilson, C. J. N., Chamberlain, C. J., Hreinsd ́ottir, S., Ellis, S., Hamling, I. J., Savage, M. K., Mestel, E. R., & Wadsworth, F. B. (2021). Volcanic unrest at Taupo ̄ volcano in 2019: Causes, mechanisms and implications. Geochemistry, Geophysics, Geosystems, e2021GC009803. The data is presented in .csv files, in the same format as MFAST output, (http://mfast-package.geo.vuw.ac.nz), in which each column is: 1. Name of the event. 2. Station code. 3. Station latitude. 4. Station longitude. 5. Event identification number. 6. Year. 7. Julian day on which the event occurred, with decimal digits giving the fraction of the day. 8. Earthquake latitude in degrees. 9. Earthquake longitude in degrees. 10. Distance between earthquake and station (km). 11. Earthquake depth (km). 12. Earthquake magnitude. 13. Back azimuth in degrees. 14. Initial polarisation of the shear wave in degrees. 15. Error of the initial polarisation in degrees, one standard deviation. 16. Start time of the selected measurement window in seconds, relative to the start of the seismogram at t = 0. 17. End time of the selected measurement window in seconds, relative to the start of the seismogram at t = 0. 18. Not used 19. Not used 20. Signal to noise ratio for this event. 21. Delay tome between fast and slow shear wave in seconds. 22. Delay time between fast and slow shear wave in seconds. 23. Angle of the orientation of the fast shear wave (φ), in degrees from North. 24. Error of φ in degrees, one standard deviation. 25. Angle of incidence at the station, measured against a horizontal plane in degrees, where 0 means vertical incidence. 26. Not used 27. Type of measurement. This field contains the measurement code that is used, the number of measurement window start times and the number of window end times. 28. Not used 29. Not used 30. Nyquist frequency of the event in Hz. 31. Evaluation of the measurement quality. 32. Lower corner frequency of the bandpass filter in Hz. 33. Higher corner frequency of the bandpass filter in Hz. 34. Angle between the initial polarisation and the fast orientation in degrees. 35. Not used 36. Not used 37. The maximum value of the eigenvalue of the corrected covariance matrix. 38. The number of degrees of freedom in the measurement. 39. The minimum value of the eigenvalue of the covariance matrix before it was scaled to have the 95% confidence level set to 1. 40. The S-wave travel time between the earthquake and the station. 41. The dominant frequency in the S wave, determined from the frequency at the maximum spectral amplitude.
Silicic caldera volcanoes are frequently situated in regions of tectonic extension, such as continental rifts, and are subject to periods of unrest and/or eruption that can be triggered by the interplay between magmatic and tectonic processes. Modern (instrumental) observations of deformation patterns associated with magmatic and tectonic unrest in the lead up to eruptive events at silicic calderas are sparse. Therefore, our understanding of the magmatic-tectonic processes associated with volcanic unrest at silicic calderas is largely dependent on historical and geological observations. Here we utilize existing instrumental, historical and geological data to provide an overview of the magmatic-tectonic deformation patterns operating over annual to 10 4 year timescales at Taupō volcano, now largely submerged beneath Lake Taupō, in the rifted-arc of the Taupō Volcanic Zone. Short-term deformation patterns observed from seismicity, lake level recordings and historical records are characterized by decadal-scale uplift and subsidence with accompanying seismic swarms, ground shaking and surface ruptures, many of which may reflect magma injections into and around the magma reservoir. The decadal-scale frequency at which intense seismic events occur shows that ground shaking, rather than volcanic eruptions, is the primary short-term local hazard in the Taupō District. Deformation trends near and in the caldera on 10 1 –10 4 yr timescales are atypical of the longer-term behavior of a continental rift, with magma influx within the crust suppressing axial subsidence of the rift basin within ∼10 km of the caldera margin. Examination of exposed faults and fissures reveals that silicic volcanic eruptions from Taupō volcano are characterized by intense syn-eruptive deformation that can occasionally extend up to 50 km outside the caldera structure, including ground shaking, fissuring and triggered fault movements. We conclude that eruption and unrest scenarios at Taupō volcano depend on the three-way coupling between the mafic-silicic-tectonic systems, with eruption and/or unrest events leading to six possible outcomes initially triggered by mafic injection either into or outside the magma mush system, or by changes to the tectonic stress state.
Last year’s rumblings beneath New Zealand’s Taupō supervolcano, the site of Earth’s most recent supereruption, lend new urgency to research and outreach efforts in the region.
Taupō is a large caldera volcano located beneath a lake in the centre of the North Island of New Zealand and most recently erupted ~1800 years ago. The volcano has experienced at least 16 periods of unrest since 1872, each of which were characterised by increased seismic activity. Here we detail seismic activity during the most recent period of unrest from May 2022 to May 2023. The unrest was notable for the highest number of earthquakes detected during instrumented unrest episodes, and for one of the largest magnitude earthquakes detected beneath the lake for at least 50 years (ML 5.7). Relocated earthquakes indicate seismic activity was focused around an area hosting overlapping caldera structures and a hydrothermal system. Moment tensor inversion for the largest earthquake includes a non-negligible inflationary isotropic component. We suggest the seismic unrest was caused by the reactivation of faults due to an intrusion of magma at depth.
Volcanic eruptions at mid-ocean ridges are rarely witnessed due to their inaccessibility, and are therefore poorly understood. Shallow waters in the Red Sea allow the study of ocean ridge related volcanism observed close to sea level. On the 18th December 2011, Yemeni fishermen witnessed a volcanic eruption in the southern Red Sea that led to the formation of Sholan Island. Previous research efforts to constrain the dynamics of the intrusion and subsequent eruption relied primarily on GPS and InSAR methods, data for which was relatively sparse. Our study integrates InSAR analysis with seismic data from Eritrea, Yemen and Saudi Arabia to provide additional insights into the transport of magma in the crust that fed the eruption. Twenty-three earthquakes of magnitude 2.1 to 3.9 were located using the Oct-tree sampling algorithm. The earthquakes propagated southeastward from north of Sholan Island, mainly between December 12th and December 13th. The seismicity is interpreted as being induced by emplacement of a ~12 km-long dike. Earthquake focal mechanisms are primarily normal faulting and suggest the seismicity was caused through a combination of dike propagation and inflation. We combine these observations with new deformation modeling to constrain the location and orientation of the dike. The best-fit dike orientation that satisfies both geodetic and seismic data is NNW-SSE, parallel to the overall strike of the Red Sea. Further, the timing of the seismicity suggests the volcanic activity began as a submarine eruption on the 13th December. The new intrusion and eruption along the ridge suggests seafloor spreading is active in this region.
The Danakil region of northern Afar is an area of ongoing seismic and volcanic activity caused by the final stages of continental breakup.To improve the quantification of seismicity, we developed a calibrated local earthquake magnitude scale.The accurate calculation of earthquake magnitudes allows the estimation of b-values and maximum magnitudes, both of which are essential for seismic-hazard analysis.Earthquake data collected between February 2011 and February 2013 on 11 three-component broadband seismometers were analyzed.A total of 4275 earthquakes were recorded over hypocentral distances ranging from 0 to 400 km.A total of 32,904 zero-to-peak amplitude measurements (A) were measured on the seismometer's horizontal components and were incorporated into a direct linear inversion that solved for all individual local earthquake magnitudes (M L ), 22 station correction factors (C), and 2 distance-dependent factors (n, K) in the equation M L logA-logA 0 C. The resultant distance correction term is given by -logA 0 1:274336 logr=17 -0:000273r -17 2. This distance correction term suggests that attenuation in the upper and mid-crust of northern Afar is relatively high, consistent with the presence of magmatic intrusions and partial melt.In contrast, attenuation in the lower crust and uppermost mantle is anomalously low, interpreted to be caused by a high melt fraction causing attenuation to occur outside the seismic frequency band.The calculated station corrections serve to reduce the M L residuals significantly but do not show a correlation with regional geology.The cumulative seismicity rate produces a b-value of 0:9 0:06, which is higher than most regions of continental rifting yet lower than values recorded at midocean ridges, further supporting the hypothesis that northern Afar is transitioning to seafloor spreading.Electronic Supplement: List of all local earthquakes used in the study with calculated local magnitudes and associated magnitude error.
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