.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "api/gallery/geophysics/plot_11_matuyama_reversed_epoch.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_api_gallery_geophysics_plot_11_matuyama_reversed_epoch.py>`
        to download the full example code or to run this example in your browser via JupyterLite.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_api_gallery_geophysics_plot_11_matuyama_reversed_epoch.py:


Matuyama's reversed epoch (1929)
================================

Motonori Matuyama measured the magnetization of basalts from Japan, Korea and
Manchuria. The youngest flows were magnetized along today's field, but older,
early Quaternary flows pointed the opposite way. He concluded that the field
had been reversed for a long time before the present one, the interval now
called the Matuyama chron. A flow is reversed when its direction lies more than
90 degrees from the present axial dipole field at the site.

.. GENERATED FROM PYTHON SOURCE LINES 12-41



.. image-sg:: /api/gallery/geophysics/images/sphx_glr_plot_11_matuyama_reversed_epoch_001.png
   :alt: Older flows are reversed
   :srcset: /api/gallery/geophysics/images/sphx_glr_plot_11_matuyama_reversed_epoch_001.png
   :class: sphx-glr-single-img





.. code-block:: Python


    import matplotlib.pyplot as plt
    import numpy as np

    from earthsciencekit.geophysics import dipole_inclination, direction_angle
    from earthsciencekit.units import convert

    normal_chrons = [(0.0, 0.773), (0.988, 1.072), (1.775, 1.934), (2.595, 3.0)]  # Ma: Brunhes, Jaramillo, Olduvai, Gauss
    rng = np.random.default_rng(1929)
    age = np.sort(rng.uniform(0.05, 2.9, 40))
    normal = np.array([any(start <= t < end for start, end in normal_chrons) for t in age])
    site = np.radians(35.0)
    present = dipole_inclination(site)
    declination = np.where(normal, 0, np.pi) + rng.normal(0, 0.15, age.size)
    inclination = np.where(normal, present, -present) + rng.normal(0, 0.1, age.size)
    angle = direction_angle(declination, inclination, 0, present)
    assert np.array_equal(angle > np.pi / 2, ~normal)
    assert np.all(angle[age < 0.773] < np.pi / 2)

    fig, ax = plt.subplots(figsize=(8, 4))
    for start, end in normal_chrons:
        ax.axvspan(start, end, color="0.85")
    ax.plot(age[normal], convert(angle[normal], "rad", "degree"), "ko", mfc="k", label="normal")
    ax.plot(age[~normal], convert(angle[~normal], "rad", "degree"), "ko", mfc="w", label="reversed")
    ax.axhline(90, color="C3", ls="--")
    ax.set(xlabel="age [Ma] (shaded: normal chrons)", ylabel="angle from present field [degrees]", title="Older flows are reversed")
    ax.legend()

    plt.show()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.090 seconds)


.. _sphx_glr_download_api_gallery_geophysics_plot_11_matuyama_reversed_epoch.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: lite-badge

      .. image:: images/jupyterlite_badge_logo.svg
        :target: ../../../lite/lab/index.html?path=api/gallery/geophysics/plot_11_matuyama_reversed_epoch.ipynb
        :alt: Launch JupyterLite
        :width: 150 px

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_11_matuyama_reversed_epoch.ipynb <plot_11_matuyama_reversed_epoch.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_11_matuyama_reversed_epoch.py <plot_11_matuyama_reversed_epoch.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_11_matuyama_reversed_epoch.zip <plot_11_matuyama_reversed_epoch.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_