<commit_before>Scripts and Data for Out-of-Sequence Shortening Calculations in the Nankai Trough, Japan
===================

Visualizations and data for http://www.geology.wisc.edu/~jkington/Kington-OOST_Paper.pdf

Abstract
--------

Out-of-sequence thrusting seaward of the Kumano Basin in the Nankai Accretionary
Prism, Japan has been a focus of extensive recent work and multiple IODP
expeditions. However, the amount of shortening and along strike motion
accommodated by the thrusts has not been studied in detail. We constrain the
total amount of shortening accommodated by the out-of-sequence thrust system
(OOSTS) in two ways. First, we compare the total shortening accommodated by all
other structures in the outer wedge to the amount of shortening predicted by
plate motions. Bed-length balancing of structures suggests that the outer wedge
has accommodated 65±14 km of shortening over the last 2.3±0.2 myr, while plate
motion models [Loveless & Meade, 2010] predict 99±10 km of convergence between
the forearc block and the subducting Philippine Sea Plate. If we assume that
all other shortening is accommodated by the out-of-sequence thrust system, this
predicts 34±17 km of shortening on the OOSTS. For the second method, we use
fault geometry and syn-kinematic forearc stratigraphy to model the magnitude
and direction of slip on the zone’s youngest structure. Modeling growth
stratigraphy within the forearc basin using inclined shear along the observed
3D fault geometry predicts 14.6±1.8 km of shortening accommodated by the
younger of the two major thrusts in the OOSTS. Additionally, the growth strata
in the forearc older than ∼0.5 Ma are best fit by oblique slip along the fault
at an azimuth of 321°, subparallel to plate motion. The growth strata also
constrain uplift of the forearc to have begun no earlier than 0.9-1.04 Ma and
to have continued until sometime more recently than ∼0.5 Ma. In contrast,
Gulick, et al [2010] concluded that uplift of the forearc began at 1.24-1.34 Ma
and ended by 0.9-1.04 Ma. Our constraints on the timing suggests that there was
a ∼0.2-0.3 myr period between activity on older and younger thrusts in the
OOSTS when shortening was primarily accommodated on structures near the toe of
the accretionary prism. Furthermore, comparing the duration of activity with
our estimates for the motion on each structure in the OOSTS suggests that each
of the two thrusts accommodated ∼65% of the total plate convergence during the
time that they were active. Finally, we propose that the activation of the
younger, landward-most thrust in the OOSTS may be related to the nearby
subduction of the Paleo-Zenisu ridge, which would have begun at ∼1.3-1.0 Ma.

Notes
-----

Most of the key functionality is implemented in the 
``fault_kinematics`` library: https://github.com/joferkington/fault_kinematics. 
The scripts in this repository handle the site and project specific
calculations and visualizations.

Requires
--------

  * Python 2.5 - 2.7 
  * Matplotlib >= 1.0
  * Numpy >= 1.1
  * Scipy >= 0.6
  * h5py >= 2.0

  * Python-geoprobe
  * <https://github.com/joferkington/fault_kinematics>
  * <https://github.com/joferkington/seismic_plotting>

  Some visualizations (e.g. ``interactive_inclined_shear.py``) require Mayavi and Tvtk.

Key Files
--------

``data.py` <https://github.com/joferkington/oost_paper_code/blob/master/data.py>`_
	Locations of datafiles and transform utilities.
``basic.py``
	A simple best-fit inversion of the amount of slip along the fault to
	restore each horizon to horizontal.  For the paper, the results are
	obtained from ``bootstrap_error.py``.
``bootstrap_error.py``
	Runs a parallel monte-carlo inversion to estimate both the amount of
	slip and the error in the estimate. This inverts for slip 200 times for
	each horizon, using boostrapping with replacement on the points in both
	the horizon and fault geometries. The results are stored in
	``bootstrap.hdf5``.
``depth_conversion_simple.py``
	Builds a 1D time-depth *for the fault surface beneath the forearc* (and
	only the fault surface beneath the forearc) using the observed fault
	geometry in both time and depth.  (We didn't have access to the
	velocity model for the 3D volume at the time.) This is then applied to
	the fault surface picked from the 2D data to convert it to depth.
	``error_ellipse.py``
``fit_shear_angle.py``
	Finds the best fitting shear angle for each horizon using a grid search.
``forearc_detail_section.py``
	Plots a detailed cross section through the uplifted forearc basin
	stratigraphy. The base plot for Figure 3 in the paper.
``interactive_basic.py``
        An interactive 3D visualization of the results. Displays the restored
        position of one of the horizons and the fault geometry and lets the
        user simulate slip on the fault.
``interactive_inclined_shear.py``
        Functions used in ``interactive_basic.py``. Displays the present day
        geometries of the fault and a horizon and lets the user simulate slip
        on the fault.  
``plot_bootstrap_results.py``
        Plots slip over time with error ellipses. Generates the base for Figure
        8 in the paper.
``plot_dip_development.py``
        Plots present-day strike and dip of forearc stratigraphy. Generates the
        base for Figure 9 in the paper.
``plot_line_balancing_and_plate_motion.py``
        Calculates shortening amounts (and errors) from line balancing and
        plots Figures 5 and 10.
``process_bootstrap_results.py``
        Calculates shortening (and errors) parallel to the section line from
        the bootstrapping results.  
``restore_horizons.py``
``sequential_restoration_cross_section.py``
``sequential_restoration.py``
        Attempt to invert for slip where the horizons are not restored
        independently.  This gives identical results as the independent version
        (``basic.py`` and ``bootstrap_error.py``). This demonstrates that the
        result is not sensitive to the fact that each horizon is restored
        independently of the one before it.
``utilities.py``
        Various utility functions.
``visualize_solution.py``

``grid_search.py``
``invert_shear_angle.py``
``plot_restored_horizon.py``<commit_msg>Added links to file descriptions<commit_after>Scripts and Data for Out-of-Sequence Shortening Calculations in the Nankai Trough, Japan
===================

Visualizations and data for http://www.geology.wisc.edu/~jkington/Kington-OOST_Paper.pdf

Abstract
--------

Out-of-sequence thrusting seaward of the Kumano Basin in the Nankai Accretionary
Prism, Japan has been a focus of extensive recent work and multiple IODP
expeditions. However, the amount of shortening and along strike motion
accommodated by the thrusts has not been studied in detail. We constrain the
total amount of shortening accommodated by the out-of-sequence thrust system
(OOSTS) in two ways. First, we compare the total shortening accommodated by all
other structures in the outer wedge to the amount of shortening predicted by
plate motions. Bed-length balancing of structures suggests that the outer wedge
has accommodated 65±14 km of shortening over the last 2.3±0.2 myr, while plate
motion models [Loveless & Meade, 2010] predict 99±10 km of convergence between
the forearc block and the subducting Philippine Sea Plate. If we assume that
all other shortening is accommodated by the out-of-sequence thrust system, this
predicts 34±17 km of shortening on the OOSTS. For the second method, we use
fault geometry and syn-kinematic forearc stratigraphy to model the magnitude
and direction of slip on the zone’s youngest structure. Modeling growth
stratigraphy within the forearc basin using inclined shear along the observed
3D fault geometry predicts 14.6±1.8 km of shortening accommodated by the
younger of the two major thrusts in the OOSTS. Additionally, the growth strata
in the forearc older than ∼0.5 Ma are best fit by oblique slip along the fault
at an azimuth of 321°, subparallel to plate motion. The growth strata also
constrain uplift of the forearc to have begun no earlier than 0.9-1.04 Ma and
to have continued until sometime more recently than ∼0.5 Ma. In contrast,
Gulick, et al [2010] concluded that uplift of the forearc began at 1.24-1.34 Ma
and ended by 0.9-1.04 Ma. Our constraints on the timing suggests that there was
a ∼0.2-0.3 myr period between activity on older and younger thrusts in the
OOSTS when shortening was primarily accommodated on structures near the toe of
the accretionary prism. Furthermore, comparing the duration of activity with
our estimates for the motion on each structure in the OOSTS suggests that each
of the two thrusts accommodated ∼65% of the total plate convergence during the
time that they were active. Finally, we propose that the activation of the
younger, landward-most thrust in the OOSTS may be related to the nearby
subduction of the Paleo-Zenisu ridge, which would have begun at ∼1.3-1.0 Ma.

Notes
-----

Most of the key functionality is implemented in the 
``fault_kinematics`` library: https://github.com/joferkington/fault_kinematics. 
The scripts in this repository handle the site and project specific
calculations and visualizations.

Requires
--------

  * Python 2.5 - 2.7 
  * Matplotlib >= 1.0
  * Numpy >= 1.1
  * Scipy >= 0.6
  * h5py >= 2.0

  * Python-geoprobe
  * <https://github.com/joferkington/fault_kinematics>
  * <https://github.com/joferkington/seismic_plotting>

  Some visualizations (e.g. ``interactive_inclined_shear.py``) require Mayavi and Tvtk.

Key Files
--------

`data.py <https://github.com/joferkington/oost_paper_code/blob/master/data.py>`_
	Locations of datafiles and transform utilities.
`basic.py <https://github.com/joferkington/oost_paper_code/blob/master/basic.py>`_
	A simple best-fit inversion of the amount of slip along the fault to
	restore each horizon to horizontal.  For the paper, the results are
	obtained from ``bootstrap_error.py``.
`bootstrap_error.py <https://github.com/joferkington/oost_paper_code/blob/master/basic.py>`_
	Runs a parallel monte-carlo inversion to estimate both the amount of
	slip and the error in the estimate. This inverts for slip 200 times for
	each horizon, using boostrapping with replacement on the points in both
	the horizon and fault geometries. The results are stored in
	``bootstrap.hdf5``.
`depth_conversion_simple.py <https://github.com/joferkington/oost_paper_code/blob/master/depth_conversion_simple.py>`_
	Builds a 1D time-depth *for the fault surface beneath the forearc* (and
	only the fault surface beneath the forearc) using the observed fault
	geometry in both time and depth.  (We didn't have access to the
	velocity model for the 3D volume at the time.) This is then applied to
	the fault surface picked from the 2D data to convert it to depth.
	``error_ellipse.py``
`fit_shear_angle.py <https://github.com/joferkington/oost_paper_code/blob/master/fit_shear_angle.py>`_
	Finds the best fitting shear angle for each horizon using a grid search.
`forearc_detail_section.py <https://github.com/joferkington/oost_paper_code/blob/master/forearc_detail_section.py>`_
	Plots a detailed cross section through the uplifted forearc basin
	stratigraphy. The base plot for Figure 3 in the paper.
`interactive_basic.py <https://github.com/joferkington/oost_paper_code/blob/master/interactive_basic.py>`_
        An interactive 3D visualization of the results. Displays the restored
        position of one of the horizons and the fault geometry and lets the
        user simulate slip on the fault.
`interactive_inclined_shear.py <https://github.com/joferkington/oost_paper_code/blob/master/interactive_inclined_shear.py>`_
        Functions used in ``interactive_basic.py``. Displays the present day
        geometries of the fault and a horizon and lets the user simulate slip
        on the fault.  
`plot_bootstrap_results.py <https://github.com/joferkington/oost_paper_code/blob/master/plot_bootstrap_results.py>`_
        Plots slip over time with error ellipses. Generates the base for Figure
        8 in the paper.
`plot_dip_development.py <https://github.com/joferkington/oost_paper_code/blob/master/plot_dip_development.py>`_
        Plots present-day strike and dip of forearc stratigraphy. Generates the
        base for Figure 9 in the paper.
`plot_line_balancing_and_plate_motion.py <https://github.com/joferkington/oost_paper_code/blob/master/plot_line_balancing_and_plate_motion.py>`_
        Calculates shortening amounts (and errors) from line balancing and
        plots Figures 5 and 10.
`process_bootstrap_results.py <https://github.com/joferkington/oost_paper_code/blob/master/process_bootstrap_results.py>`_
        Calculates shortening (and errors) parallel to the section line from
        the bootstrapping results.  
`restore_horizons.py <https://github.com/joferkington/oost_paper_code/blob/master/restore_horizons.py>`_
`sequential_restoration_cross_section.py <https://github.com/joferkington/oost_paper_code/blob/master/sequential_restoration_cross_section.py>`_
`sequential_restoration.py <https://github.com/joferkington/oost_paper_code/blob/master/sequential_restoration.py>`_
        Attempt to invert for slip where the horizons are not restored
        independently.  This gives identical results as the independent version
        (``basic.py`` and ``bootstrap_error.py``). This demonstrates that the
        result is not sensitive to the fact that each horizon is restored
        independently of the one before it.
`utilities.py <https://github.com/joferkington/oost_paper_code/blob/master/utilities.py>`_
        Various utility functions.
`visualize_solution.py <https://github.com/joferkington/oost_paper_code/blob/master/visualize_solution.py>`_

`grid_search.py <https://github.com/joferkington/oost_paper_code/blob/master/grid_search.py>`_
`invert_shear_angle.py <https://github.com/joferkington/oost_paper_code/blob/master/invert_shear_angle.py>`_
`plot_restored_horizon.py <https://github.com/joferkington/oost_paper_code/blob/master/plot_restored_horizon.py>`_
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