Fun_SetInvFaultUpdate.m

function [newGrid, newSource, newIndex] = Fun_SetInvFaultUpdate( ...
    NormSlip, oldGrid, oldSource, gridsize, SDR, loca, ...
    epicenter, depth, IndexEQ)
% =========================================================================
% Update the fault grid based on the principal rupture region, then remove
% rows that lie above the free surface
[newGrid, newSource] = subfaults_making(NormSlip, oldGrid, oldSource);

% Generate depths for the proposed updated fault grid.
[~, newDep] = get_subloca( ...
    SDR, newGrid([2, 1]), gridsize, [1, newSource([2, 1])], loca, epicenter);

newIndex = (newSource(2) - 1) * newGrid(1) + newSource(1);
% Shift the entire fault plane so that the source subfault matches the
% prescribed hypocentral depth.
newDep = newDep + (depth(IndexEQ) - newDep(newIndex));

%% ------------------------------------------------------------------------
% Remove dip-direction rows that are above the free surface
nRemoveTop = ceil(sum(newDep(:) < 0) / newGrid(2));

if nRemoveTop > 0

    newSource(1) = newSource(1) - nRemoveTop;
    newGrid(1)   = newGrid(1) - nRemoveTop;

    if newSource(1) < 1 || newGrid(1) < 1
        error(['Fault-grid adjustment removed the hypocentral row ', ...
               'or all dip-direction rows.']);
    end
end
newIndex = (newSource(2) - 1) * newGrid(1) + newSource(1);
end