Progress!

 
 
<H2>2016.11.14</H2>
<H2>Progress!</H2>
<ul>
<li>We have been a really good team on this ship. Dr. Barnes has done a terrific job preparing for our coring cruise. The geospatial data that he has collected and gained access to over the years is, by far, the most comprehensive and detailed (and of highest resolution) of any submarine data that I have used to plan a coring cruise. He has conducted hydrodynamic modeling to estimate potential flow paths. He has mapped the seafloor geomorphology to determine regions of erosion vs. deposition. There are still a great many unknowns, but having this knowledge in the forefront of the planning process clearly gives one a heads up on being able to select good coring sites. Of course, I only have the ability to recognize this due to the training that I have had, initially from Dr. Chris Goldfinger on my maiden research cruise offshore Sumatra. I have supplemented this experience elsewhere,
along different margins. </li>
<li>We have been traversing the fold and thrust belt / continental slope northwards. As I mentioned before (here or elsewhere), we test the hypothesis that the triggering mechanisms for the turbidity currents that lead to the turbidites that we core are triggered by earthquakes. We use one or more of the following methods as part of this test: (a) confluence tests using turbidite counts above a temporal/stratigraphic datum or correlations and (b) isolated source area tests using correlations. We are coring in various channel systems that have isolated source areas. We are looking in piggyback slope basins, also with (hopefully) isolated source areas. </li>
<li>We hope to find along-margin segments of the Holocene (at least) sedimentary record that are somewhat unique from each other so that we might be able to compare how the earthquake record might vary along strike. In the northern Hikurangi Trough, the subducting plate as abundant seamounts that are affecting the plate interface. In the southern Hikurangi Trough, the downgoing plate is smoother with a thicker sedimentary section (up to 6 km, Barnes p.c.). Generally, we think that this would result in larger magnitude earthquakes in the south and smaller magnitude earthquakes in the north. However, this is still a debated topic in plate tectonics. There are some indications that these two parts of the subduction zone are tectonically different. Wallace et al. (2014) present a paper about tsunami potential and they show that regions of slow slip earthquakes are much further up-dip
(shallower on the subduction zone fault) in the north, than they are in the south (in the figure, the green contours are the slip contours for the slow slip earthquakes). Also, they show a figure that displays the coupling ratio (the proportion of the plate convergence that is accumulated as strain along the fault). I include this figure in this post (red is more highly coupled, blue is less coupled). </li>
 
<li>I am still navigating how to post to my blog with limited internet access. I am attaching an image to an email that I am using to post to my blog. I also include some html that links to the image that I posted online last week.</li>


<a href=" http://earthjay.com/cruises/2016_new_zealand/literature/wallace_etal_2014_earthquake_tsunami_potential_hikurangi_fig_03.PNG">

<img src=" http://earthjay.com/cruises/2016_new_zealand/literature/wallace_etal_2014_earthquake_tsunami_potential_hikurangi_fig_03.PNG">
</a>


<li>Below is the figure caption for the above image (Wallace et al., 2014).</li>
<blockquote>
Interseismic coupling coefficients (see red to blue scale) from campaign GPS measurements (Wallace et al., 2012a) and cumulative slip in slow-slip events (SSEs) from 2002–2012 (green contours, labeled in mm; from Wallace et al., 2012b). Dashed green contours show slip in a deep central Hikurangi SSE in 2008 (Wallace and Eberhart-Phillips, 2013). Dashed black contours showing the depth to the subduction interface (in km below sea level) are from Ansell and Bannister (1996), and thus present an earlier version of the interface geometry compared to the more recent one shown in Figure 1 from Williams et al. (2014).

</blockquote>


<li>The GPS inversion that Wallace and her colleagues use to infer plate coupling is but a snap shot of a moment in time. We do not know if this represents the long term behavior of the fault nor how it might relate to earthquake recurrence, magnitude, segmentation, etc. It seems reasonable, but coming up with a Holocene earthquake record will be a big contribution to answering this question. </li>
 
<li>This morning there was a large magnitude earthquake. There is talk here in New Zealand (GNS) that there may be as much as 10 meters of slip along one of the major thrust faults in this region. There have been observations of surface rupture on multiple different faults (some are strike-slip). This is a very interesting earthquake and is quite complicated. Unfortunately two people died, but we are lucky that this earthquake occurred in a relatively sparsely populated area. </li>
<li>Needless to say, we will be modifying our plans slightly to take advantage of being on a research vessel at this moment in time, with a coring crew ready to take cores near the earthquake region. We are currently getting information from GNS (the New Zealand geological survey) and NIWA (the organization that Dr. Barnes is with, who runs the R/V Tangaroa). This information will inform us as to the best way that we might decide where to go and what data to collect. We will be taking cores in the region of today's earthquake. We may also collect some additional bathymetry data. We had some core sites located in this region, but they were a lower priority due to the complications of the geomorphology and faulting in this region. However, given that we just had an earthquake of a size that could trigger submarine landslides (there is an estimate that there are over 100,000 subaerial
landslides), as long as we core in the correct place, we should be able to core a seismoturbidite triggered by this earthquake. </li>
</ul>
 
<H2>Science Crew</H2>
<ul>
Below is a list of the science crew aboard the R/V Tangaroa:
<li>Philip Barnes </li>
<li>Alan Orpin </li>
<li>Peter Gerring </li>
<li>John Mitchell </li>
<li>Will Quinn </li>
<li>Geoffroy Lamarche </li>
<li>Susi Woelz </li>
<li>Jamie Howarth </li>
<li>Jason Patton </li>
<li>Sam Davidson </li>
<li>Simon Banks </li>
<li>Jenni Hopkins </li>
<li>Monique Mckeown </li>
<li>Aratrika Ganguly </li>
</ul>