Earthquake Shift

[2oldfarts (the rockhounders)]

Last weekend we were on a road in southern Utah and came upon a sign for "Road Damage". There was a drop of about 2 1/2 to 3 inches. The road had uplifted that much. About 100 yards further along the road there was a lateral shift in the pavement. The road had a double yellow line at this point and the shift had moved the pavement enough that the right side yellow line now lined up with the left side yellow line. Unfortunately I wasn't able to get a picture at this time.

 

My question is this.... If I were to recover any benchmark near this shifting, how would I classify the recovery? Good, Poor, other?

 

The ground has moved enough to move the mark out of position, so would it qualify as "destroyed"?

 

John

[+Kewaneh & Shark]

Unless the physical monument was damaged, I would log it as you find it (ie. good, fair, poor, destroyed), and not be too concerned with any possible earth movement displacement, unless you can prove that it did in fact move. If you have concerns about movement, just note them in your log.

 

From a horizontal standpoint, considering that many of the lat/long coords that are published with many of the benchmarks are 'scaled', a tectonic shift of a few inches or feet really won't change things. Some of the more recently set marks, which were set with high-precision, GPS equipment, would need to be re-measured with similar equipment (not a recreational GPSr) to determine any movement.

 

Vertically, a mark would have to be re-leveled to from another benchmark to determine any movement (and the assumption made that the other mark has remained motionless).

 

Using movement as a qualification to determine a mark's condition, particularly considering 'destroyed', would obliterate many (most) of the marks in my area. I frequently work near the San Andreas Fault and the land moves very frequently. Sometimes enough to give a person IMMEDIATE and lasting motion sickness. (In addition, the underground aquifers 'pump' the ground like a balloon several feet up and down every year.) Movement happens. We just use the published data and run with it.

 

- Kewaneh