Earth in Motion Summary_mori_wallace

8/11/2019 Earth in Motion Summary_mori_wallace

1/16

Proposals in the System:

Hikurangi slow slip- 781-MDP & 781A-Full, Riserless drilling and ObservatoryPhase

Proposals in the process of being developed:

Hikurangi deep riser drilling phase

Ideas for New Proposals:

Brothers Volcano (Cornel de Ronde)

Tuaheni Slides (Ingo Pecher)

Porangahau Fluid Flow & Slow Slip (Ingo Pecher)

Near Trench Axis drilling-comparative study of Japan, Hikurangi, Costa Rica,

Sumatra (Shuichi Kodaira)

Earth in Motion Summary- Jim Mori, Laura Wallace


2/16

Proposals in Progress

Hikurangi Slow Slip

Understand the causes of slow slip events

Drilling target is an interface dominated by aseismic

creep (in distinct contrast to Nankai)

Coring and logging will provide information about

physical conditions in region within and above slow

slip events. Incoming plate section will reveal

protolith of rocks in the SSE source further down.

Monitoring changes in strain, tilt, seismicity, andfluid pressure, flow rates, and geochemistry during

slow slip events


3/16

3

Comparison between Japan trench and Hikurangithis

could make Hikurangi a compelling riser target to help

undertand Japans subduction zones

Japan Trench Hikurangi

Fault depth 10 15 km 5 15 km

Mw 6.8 7.0 6.56.8Duration 20 40 days 14 35 days

Yoshihiro Ito


4/16

Main discussion points for further developing

Hikurangi slow slip project

Riser proposal to reach source of slow slip events ( ~ 5.5 km )

Plan to submit riser proposal in April 2013

Need to coordinate funding for observatory (riserless and riser),3-D site survey, 3D VSP, OBS+pressure gauge deployment

Identify fault(s) of large earthquakes and slow slip events

Great interest in physical mechanisms, friction characteristics,

fluid conditions, comparisons to other regions (Tohoku)

Important to obtain sample of fault zone (difficult coring)

Fluid and Pressure monitoring in deep borehole

Need some casing deformation measurement


5/16

New Ideas for proposals

Brothers Volcano- Cornel de Ronde

Volatiles coming to seafloor, end members of flow

rates and fluid composition at one volcano

Workshop in Europe in November

Proposal submission in April 2013?

Caldera formation

Exsolved gas from magma

Formation of hydrothermal minerals

Biological communities


6/16


Tuaheni Slides- Ingo Pecher

Possible slow moving landslides in region of proposed781-Adrilling transect

Over pressured fluids and gas from hydrates may

cause hydrofractures, producing landslide planesin regions of hydrates

(Usually BSR are thought to be slide plane)

MeBo, R/V Sonne 70? mcores scheduled in 2015?

APL Proposal for 150-200 m boreholes, LWD and pressure cores

Mechanisms of slides

Role of overpressurization from hydrates


7/16


8/16


9/16


Porangahau Ridge Fluids (central Hikurangi margin)

Large scale gas volumes outside of GHSZ (Gas Hydrate Stability

Zone)

South of Hikurangi proposal area, slow slip interval different

more fluids

Episodic slow slip events may cause fluid flow.

Transient fluid flow suspected from heat flow anomaly, resistivity,

seismic velocities.

Propose boreholes with LWD (temperature), pore water chemistry,

pressure cores, observatory (too much for APL?). Could this be a

MeBo (+MeBo observatory), or potentially a future (well down the

track) JR proposal? Probably needs more surface investigations.

Constrain fluid flow budgets, fluid sources during slow-slipTest model


10/16

Seafloor thermal gradient

Massive discrepancy to BSR thermal gradient

May point towards transient anomaly (i.e., advective heatflow pulse)

(but may be caused by bottom-water temp. fluctuations)


11/16

(Plaza Faverola et al., in prep.)

Transient fluid-flow anomaly,

Fluids probably from depthof subduction interface

Possible fluid

migration paths

Slow-slip


12/16

New Ideas for proposalsComparisons of near trench axis drillingShuichi Kodaira

(Hikurangi, Tohoku, Nankai, Costa Rica, Sumatra)

Drilling of sediments at toe of thrust preserveshistory of previous earthquakes

Shallow holes (~100-200 meters) and piston coring

Alternate site HSM10-A in 781-A near toe, could drill ~200 m during

drilling for 781-A. Submit MSP proposal to use MeBo to do along

strike transect of ~200 m cores through Hikurangi toe

Understand the near trench earthquake rupture history Slip behavior of splay faults (vitrinite reflectance, turbidite

paleoseismology, others?)

Need to modify current conceptual model for subduction

interface behavior and shallow seismic faulting on megathrust

Slip in this region controls tsunami size Importance for hazards


13/16

IODP

Trench-filled sediment preserve a long term record of slip-

to-the-toe earthquake

Along trench axis drilling transect to spatial

and temporal record of slip-to-thetoe

earthquake


14/16

Slip at a toe in the Nankai TroughSakaguchi et al., 2011

High vitrinite reflectance;evidence of frictional heating

at the frontal thrust


15/16

Is there evidence for slipto the toe at Hikurangi?

Would also provide a

nice compare/contrastto Nankai (southHikurangi) and Tohoku(north Hikurangi)

Potential for tying thisinto a global study ofnear-trench seismicbehavior (Sumatra,Costa Rica, others?)

Hikurangi cores could bedone with MeBo as aMSP proposal+during781-A leg for N.Hikurangi


16/16

Proposals in progress/new ideas What to do?

Hikurangi Riser proposal Develop and submit riser proposal in

April 2013

Brothers Volcano Workshop in Europe, November 2012.

Possible JR pre-proposal (or full proposal

if mature enough??) for April 2013.

Tuaheni Slides (Hikurangi margin) Submit APL for 781-A drilling. MeBo

coring will happen in the area in 2015

Porangahau Fluids Possible MeBo proposal? Ideas around

this still need some development. May

require some form of observatory.

Comparative trench axis study: along-

strike transect of Hikurangi thrust front

Submit MSP proposal (to use MeBo)+we

will try to do shallow drilling (~200 m) at

north Hikurangi toe during the 781-A

riserless drilling

Earth in Motion Summary_mori_wallace

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