Research ArticleGEOPHYSICS

Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand

See allHide authors and affiliations

Science Advances  03 Jun 2016:
Vol. 2, no. 6, e1600288
DOI: 10.1126/sciadv.1600288
  • Fig. 1 Location maps showing the North Island of New Zealand and the study area at the northern end of the Taupo Volcanic Zone.

    (Left) Color-shaded relief map of the North Island of New Zealand indicating the study area (black box) and boundaries of the currently active TVZ [<300 thousand years ago (ka); solid blue line] and old TVZ [>300 ka; dashed blue line). (Right) Color-shaded relief of the study area highlighting the location of the modern TVZ (gray transparency), Okataina and Rotorua Caldera boundaries (blue dashed lines), and the relocated 2005–2009 Matata earthquake swarm, which are color-coded by year. The dashed box indicates the region shown in Fig. 4. The moment tensor (MT) solution for the largest event is shown by the beach ball. The inset in the top left shows the cumulative number of earthquakes during the sequence.

  • Fig. 2 Surface velocities derived from InSAR, leveling, and GPS data over the Bay of Plenty coast.

    (A and B) InSAR time series for scatterers (red circles) colocated with the two CGPS sites (RGOP and RGMT) along with the GPS velocities converted into the satellites LOS. (C) Mean LOS velocities derived using 32 Envisat SAR images as described in the main text. The black lines indicate mapped active faults. The black dashed circle shows subsidence associated with the Kawerau geothermal power plant. The black, white, yellow, and red arrows show the velocities for the two continuous (RGOP and RGMT) and campaign (EAY8) GPS sites (circles and lines show the 95 and 68% confidence levels for horizontal and vertical velocities, respectively) for the two periods described in the main text. The colored triangles show the GPS displacements (15) at campaign and continuous sites converted into the satellite’s LOS. The blue arrows show the velocities derived from leveling data collected in 1950 and 1978. The image shown in the black box shows the errors associated with the LOS displacements shown in the main figure.

  • Fig. 3 Observed, modeled, and residual velocities based on the best-fitting tensile dislocation model.

    The black and red arrows show the observed horizontal and vertical velocities, respectively. The white and yellow arrows show the modeled horizontal and vertical velocities, respectively. The black and white arrows in the residual panels on the right hand side of the figure show the horizontal and vertical residuals, respectively. The black dashed line marks the edge of our best-fitting sill source, and the black dot shows the location of the Mogi source. The red dashed line in the first panel shows the boundary of the present-day TVZ.

  • Fig. 4 Stress change and b value analysis of the Matata earthquake swarm.

    (A) Coulomb failure stress (CFS) change calculated for each of the earthquake epicenters of the 2005–2009 Matata earthquake swarm based on our best-fit source model (gray rectangle) and rake of −100°. (B) Estimate of the b value for the Matata earthquake swarm as described in the main text based on a node radius of 2 km. (C) Graph showing the percentage of events within the swarm with positive stress changes against rake direction for our best-fit Mogi and sill sources. The histogram shows number of events and their rake (45° bins) for events with MT solutions.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/6/e1600288/DC1

    fig. S1. Baseline time plot showing the distribution of ALOS and Envisat SAR images (red circles circles) and interferograms (black lines) used in the analysis.

    fig. S2. Mean LOS velocities derived using 32 Envisat SAR images of the study region and two offshore islands.

    fig. S3. East, north, and vertical displacements recorded at RGMT and RGOP.

    fig. S4. Mean LOS velocity derived from ALOS SAR data.

    fig. S5. Distribution of model parameters for the Mogi and sill sources.

    fig. S6. Cross section through the Matata earthquake swarm along the line A-A′ indicated in the panel on the right of the figure.

    fig. S7. Relocated earthquakes from the 2005–2009 Matata earthquake swarm, which are color-coded by year, and available MT solutions for the larger events.

    fig. S8. Cumulative number of earthquakes and b value estimates for the Matata earthquake swarm.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Baseline time plot showing the distribution of ALOS and Envisat SAR images (red circles circles) and interferograms (black lines) used in the analysis.
    • fig. S2. Mean LOS velocities derived using 32 Envisat SAR images of the study region and two offshore islands.
    • fig. S3. East, north, and vertical displacements recorded at RGMT and RGOP.
    • fig. S4. Mean LOS velocity derived from ALOS SAR data.
    • fig. S5. Distribution of model parameters for the Mogi and sill sources.
    • fig. S6. Cross section through the Matata earthquake swarm along the line A-A′ indicated in the panel on the right of the figure.
    • fig. S7. Relocated earthquakes from the 2005–2009 Matata earthquake swarm, which are color-coded by year, and available MT solutions for the larger events.
    • fig. S8. Cumulative number of earthquakes and b value estimates for the Matata earthquake swarm.

    Download PDF

    Files in this Data Supplement:

Navigate This Article