[BUG FIX] Get elevation used bottom faces when BOTTOM_FREE_SURFACE=.true. & t0 assumed hdur is half duration even though USE_RICKER is true.

[lsawade]

Elevation

When

BOTTOM_FREE_SURFACE             = .false.

the faces of the bottom elements are being prepended to the free surface elements. As a result the optimized get_elevation method that use free surface horizontal position, will check the bottom surfaces first. This fix skips those elements if BOTTOM_FREE_SURFACE = .false..

T0 for CMT+Ricker

This unrelated bug assumed that the CMTSOLUTION's half-duration is a indeed a half-duration, even though the

USE_RICKER_TIME_FUNCTION        = .true.

setting assumes it to be f0. As a result for very small f0 (big pulse width) the start time is very close to 0.0 instead of starting much earlier.
This PR fixes that by using the same t0 computation as the FORCESOLUTION's Ricker wavelet.

[lsawade]

FYI, @Rohit-Kakodkar, @icui

[codecov]

Codecov Report

❌ Patch coverage is 69.23077% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.79%. Comparing base (21e40fd) to head (4a038bb).

Files with missing lines	Patch %	Lines
src/specfem3D/get_cmt.f90	33.33%	2 Missing ⚠️
src/specfem3D/get_elevation.f90	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #1869      +/-   ##
==========================================
- Coverage   40.79%   40.79%   -0.01%     
==========================================
  Files         276      276              
  Lines       65953    65963      +10     
  Branches    10577    10581       +4     
==========================================
+ Hits        26906    26910       +4     
- Misses      39033    39039       +6     
  Partials       14       14              

Flag	Coverage Δ
coverage-testname-	40.79% <69.23%> (-0.01%)	⬇️

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[danielpeter]

thanks 🙏 Lucas!