• Time (at epicenter (ast)	position lat,long	Distance to AO KM,bearing	depth KM	Magnitude
  23:23:40	19.077  ,-67.2701	97.6km,326deg	10	6.0
  23:32:41	19.0225,-67.2081		5	5.06

  
  

• Page 1:
• The tiedown tensions are measured once a second.
  
• The horizontal scale is hour of day AST.
• Top: tiedown tensions during quakes
• black: td12
• red: td4
• green: td8
• The purple vertical lines are the earth quake time at the epicenter.
• frame 2-4 blowup of the  individual td tensions
• I've removed the mean value using data prior to the first quake.
• A blue line is over plotted through 0 (the original tension)
• td8 did not return to the tension prior to the quake.
• On this tiedown only one of the load cells  was  working (so i doubled the value of the other one)
• I don't know if the offset is a problem in the main cables, or the td yoke readjusting itself.
  
• The first quake is obvious, the 2nd quake did not register.
• Page 2:
• top: delay from 6.0 epicenter to AO in seconds
• The purple line is the quake at the  the epicenter (0 time)
• We start to see motion about 23 seconds after the quake at the epicenter.
  
• The quake had to travel 97 km horizontally and 10km vertically.
• This also includes the time for the tower oscillation to propagate to the td cables.
• The blue vertical lines were used to compute the spectra in the bottom frame (180 secs of data).
  
• Bottom: spectrum of oscillations
• 180 seconds of data was used to compute the power spectrum.
• The sampling freq is 1 Hz so the max freq is .5Hz
• The time base is determined by the little star computer. The samples are probably stable over 180 secs, but the sample rate may be a little off from 1 second.
• Td 12 had the largest value at .335 Hz. .361 Hz is the 2nd strongest (with all td having it).
  

Summary

• A 6.0 magnitude quake occurred 23:23:40 on 23sep19. It was 97 km from AO with a bearing of 326 deg
• The tiedown tension began to oscillate about 23 seconds later.
  
• A 5.0 quake occurred 9 minutes later close to the same position. It was not seen in the td tensions.
  
• The telescope was locked for tropical storm karen with az=57.5,gr=8.4769 and ch=8.8302
• The strongest oscillations were:
• .335 Hz. mainly td 12
• .361 Hz, all 3 td.
• After the oscillations, td 8 remained 400 lbs above the pre oscillation position.
• this could be a problem with the cables
• Or it could be that yoke that holds the 2 cables shifted a bit (only the tension from 1 cable was available)
  

up to oscillations
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