tiedown tensions during 16may10 earthquake
There was a 5.8
magnitude earthquake on 16may10
- time: 01:16:10 AST (puerto rican seismic net time for earthquake
- earth quake:18.40 N, 67.07 w, 34 km west of Ao (5 km from moca)
- ao: 18.344289N 66.752778W
- Depth: 113 km
- az=57.339, dome=8.3825, ch=8.835. stationary during the
earthquake (doing drift scans).
The puerto rican seismic network accelerometer located at AO showed the
The graph shows the tiedown tension vs time during
the earthquake (.ps) (.pdf):
- The accelerometer definitely went off scale...
- The colored plots are the total tension on td12 (black), td4
(red), td8(green) in kips.
- The x axis is seconds since the reported time of the quake (34 km
away).. 01:16:10 AST.
- Data is sampled once a second.
- Page 1: tiedown tension vs time
- The kips in each tiedown vs time.
- remove the median value for each tiedown an add 2 kip offsets
- Total tdkips on platform vs time (kips from all 3 tiedowns
- Page 2: oscillation frequencies.
- data from times 40 to 150 seconds was transformed to measure
the oscillation freq.
- The 3 colors are td 12 white, td4 red, td8 green.
- Two frequencies were found:
- .368 hz (2.7 seconds) this was seen in previous measurements.
- .291 hz (3.4 seconds). .291 hz is probably an alias from the
1 second sampling. The true freq is probably (.5 +(.5-.291)= .7 hz.