Stochastic Ground Motions
-------------------------

This panel allows users to generate synthetic ground motions for a
target seismic event. In order to do so, the stochastic ground motion
model is selected from the ``drop-down menu``, which is as shown
in :numref:`fig-stochasticVlachos-event`. Two stochastic motion models are currently available:
Vlachoes et al. (2018) :cite:`vlachos2018predictive` and  Dabaghi \& Der Kiureghian (2014, 2017, 2018)
:cite:`dabaghi2014stochastic,dabaghi2017stochastic,dabaghi2018simulation`. Depending on the 
model selected, the user will be asked to enter values for a number of parameters that are
used to generate a seismic event. For the Vlachos et al. model users are required to input the ``moment magnitude``, ``site to rupture distance`` and the ``average shear wave velocity``.

.. _fig-stochasticVlachos-event:

.. figure:: figures/stochasticVlachos.png
	:align: center
	:figclass: align-center
	:width: 80%

	Vlachos et al. (2018) model inputs.

.. _fig-stochasticDabaghi-event:


For the Dabaghi and Der Kiureghian model geometric directivity parameters, as shown in :numref:`fig-dabaghi`, required by the Dabaghi and Der Kiureghian model are described completely in Somerville et al. (1997) :cite:`somerville1997modification`.

.. _fig-dabaghi:

.. figure:: figures/stochasticDabaghi.png
	:align: center
	:figclass: align-center
	:width: 80%

	Dabaghi & Der Kiureghian (2018) model inputs.


Additionally, users can provide a seed for either model if they desire the same
suite of synthetic motions to be generated on multiple occasions. If
the seed is not specified, a different realization of the time history
will be generated for each run. The backend application that generates
the stochastic ground motions relies on **smelt**, a modular and
extensible C++ library for generating stochastic time histories. Users
interested in learning more about the implementation and design of
**smelt** are referred to its `GitHub Repository <https://github.com/NHERI-SimCenter/smelt>`_.

All input parameters can be specified as **random variables** by entering
a string in the parameter field. Please note that information for the
inputs that are identified as random variables needs to be provided in
the **UQ** tab.

.. .. bibliography:: ../../../../references.bib