Research ArticleGEOPHYSICS

Unusual kinematics of the Papatea fault (2016 Kaikōura earthquake) suggest anelastic rupture

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Science Advances  02 Oct 2019:
Vol. 5, no. 10, eaax5703
DOI: 10.1126/sciadv.aax5703
  • Fig. 1 Map of the 2016 Kaikōura earthquake and surrounding area.

    (A) Transpressional tectonic setting of the northeastern South Island of New Zealand. (B) Map of surface ruptures from the 2016 Mw 7.8 Kaikōura earthquake, shown in bold black lines with the Papatea fault in red (8, 28). Dots represent scaled relative energy release from back-projection results (15) and are colored by time since rupture onset. Mapped active faults that did not rupture during the Kaikōura event are indicated by thin black lines (28).

  • Fig. 2 3D displacement fields around the Papatea fault with sample fault-perpendicular profiles.

    (Left) E-W, (middle) N-S, and (right) up-down surface displacement fields around the Papatea fault from (A) SAR measurements [~330 m × 450 m pixel resolution, from Hamling et al. (4)] and (B) D-lidar calculations (25 m) within the dashed line polygon. Positive displacement directions are east, north, and up. Coarser displacement pixels outside the polygon of double lidar coverage are SAR measurements (4). G.S. labels the location of the George Stream. Thick black lines are Papatea surface ruptures. (C to H) Example 100 m × 900 m fault-perpendicular profiles [black rectangles in (B)] through the x (left), y (middle), and z (right) lidar surface displacement fields. The vertical axis is displacement, and the horizontal axis is distance, both in units of meters. Each black dot is a single-cell displacement, vertical dashed red lines show the fault scarp, and horizontal red lines show extrapolated linear fits of chosen data points with 50% confidence bounds (dashed).

  • Fig. 3 Fault kinematics from rupture profiling.

    Lidar-derived net slip (red) and fault dip (blue) measurements for the (A) main strand, (B) Wharekiri trace, and (C) Edgecombe and Wainui traces of the Papatea rupture. Uncertainties in slip (pink bars) are calculated from 50% limits in displacement drawn from each swath profile. Uncertainties in fault dip (light blue bars) are ±1 σ values of a distribution of dips yielded from a Monte Carlo simulation. Lateral and vertical slip components along strike of the Papatea fault strands (black datapoints, with ±2 σ uncertainties) and from field and lidar elevation change measurements (28) (purple datapoints with uncertainties where available) for the (D and E) main strand, (F and G) Wharekiri trace, and (H and I) Edgecombe (sinistral, solid triangles) and Wainui (dextral, open triangles) traces. Distances along the horizontal axes are from north to south of each fault trace and correspond to the 1-km markers (gray dots) in Fig. 4.

  • Fig. 4 Map of the Papatea fault zone.

    Lidar-derived fault slip vectors (arrows) colored by plunge, showing hanging wall motion relative to footwall (note vectors flip with changing dip direction). Slip vectors were measured from swath profiles taken perpendicular to the simplified fault traces in red, which closely approximate the published, mapped fault traces shown in black (28). Gray dots along the red line mark 1-km distance increments along each fault strand (starting from 0 km at each northern end) and correspond to the horizontal axes in Fig. 3. The black dashed line polygon shows the region of double lidar coverage considered in this study. Field measurement localities (28) are indicated by brown plus signs.

  • Fig. 5 Comparison of lidar-derived 3D displacement field to elastic-modeled surface deformation around the Papatea fault.

    (Left) E-W, (middle) N-S, and (right) up-down (A) elastic model and (B) observed surface displacement fields around the Papatea fault. In (A), we use nine rectangular dislocations (numbered in white circles) embedded in an elastic half-space (14) to a depth of 10 km, imposing values of dip, rake, and slip that are representative of our lidar profiling measurements (see table S2 for model inputs). The black lines show the model fault trace, and dashed black lines show the extent of the double lidar coverage. The black lines in (B) show the mapped fault traces. Black vectors overlying the up-down displacement fields indicate horizontal displacements calculated using a block mean of dimension 400 m by 400 m.

  • Fig. 6 Schematic diagram of the Papatea block and neighboring ruptures within the large step-over of the Kaikōura earthquake.

    Solid black lines indicate approximate mapped faults (8, 24, 28). Dashed gray lines indicate possible fault rupture locations (21). The black arrows near the Papatea fault demonstrate the observed horizontal displacement. The gray shaded region represents the area of the large vertical uplift that was forced to “pop up” during the earthquake due to a localized space problem caused by neighboring ruptures.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/10/eaax5703/DC1

    Fig. S1. SAR- and lidar-derived ground displacements.

    Fig. S2. Kinematics of the coastal Papatea fault zone.

    Fig. S3. Comparison of lidar-derived 3D displacement field to elastic modeled surface deformation around the main strand surface rupture with listric structure below.

    Fig. S4. Comparison of lidar-derived 3D displacement field to elastic modeled surface deformation around the main strand surface rupture with Jordan and Kekerengu ruptures.

    Fig. S5. Comparison of lidar-derived 3D displacement field to elastic modeled surface deformation around the main strand surface rupture with plate interface below.

    Table S1. Kinematic parameters from rupture profiling.

    Table S2. Elastic forward model parameters to produce figs. S3 to S5.

    Sparse ICP code and documentation

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. SAR- and lidar-derived ground displacements.
    • Fig. S2. Kinematics of the coastal Papatea fault zone.
    • Fig. S3. Comparison of lidar-derived 3D displacement field to elastic modeled surface deformation around the main strand surface rupture with listric structure below.
    • Fig. S4. Comparison of lidar-derived 3D displacement field to elastic modeled surface deformation around the main strand surface rupture with Jordan and Kekerengu ruptures.
    • Fig. S5. Comparison of lidar-derived 3D displacement field to elastic modeled surface deformation around the main strand surface rupture with plate interface below.
    • Table S1. Kinematic parameters from rupture profiling.
    • Table S2. Elastic forward model parameters to produce figs. S3 to S5.

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    Other Supplementary Material for this manuscript includes the following:

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