Do corners move?
I've been asked that a few times and my answer is a conditional yes.
So I'm doing a survey right now that is in lowlands along a large river. Ground is mostly glacial silt and wind blown loess. Some of the best farmland in the State of Alaska. I have work in the area going back to 2004 but the most recent work in the area was done in 2016/2017. As a side, it's along the 4th Standard Parallel so staggered sections. Not many of the original GLO 1914 corners remain. I went back this week and using the same control point for the base, found I was missing everything tied in the area by .3-.4' in a north/south direction. First inclination was that our control point had been disturbed. A lengthy static session showed it to be stable with very little discrepancy from past sessions. So what gives? Well, as best I can figure, back on November 30, 2018, we had a 7.1 earthquake and given the water saturated soils, as far as I can tell, that entire body of land moved south a bit under half a foot. Kind of cool having a ring side seat and being in a position to be able to actually measure that change. In other areas some distance from this location, I've had control points that were shifted, I assume by the same quake, by upwards a foot horizontally. Terra firma ain't all that firm.
The San Andreas fault runs through the northeast quarter of a section I surveyed in. The northeast section corner is definitely moving relative to the rest of the section.
Interesting... I have never been involved with seismic shifts nor their results on real property. Is there case law or reference materials available that gives guidance on this situation?
I survey along the Ohio river and saw a 6 foot change in my own monuments over the course of about 8 years in between surveys. The river eats at the bank and from the bluff down there is a periodical slip. Houses are not stable unless piered to a depth of 24' or more. One guy chained his house to a large tree nearby, not that it was doing any good. Everything in the top 15-20' was more or less moving together but the bottom maybe more than the top because things were leaning away from the river and back towards the bluff. The bank is staying in the same location but keeps getting refreshed with new dirt from uphill.
In Joannou v. Rancho Palms Verdes, 219 Cal. App. 4th 746 (2013) the appellate court holds that the Cullen Earthquake Act only applies to sudden movements as a result of a disaster. Gradual movements are not included. This does not mean there is not another remedy available in cases of gradual movement just that Cullen does not apply. The Act provides for a Court process to adjust boundaries and vacate right of ways in cases where an earthquake has suddenly shifted the ground.
Terra firma ain't all that firm.
I just want to say thank you for posting this post. It's something we have known about, but to deal with it practically and effectively, that's a challenge.
Seismic or not, yet they move, every time they are perpetuated.
I've got one right now where the case is supposedly empty, but a helpful crew actually staked for the historical record point and found it, under the concrete street and somewhere northwest of the mon case. Trouble is that they are the only people to dig that up in the last 50 years and everyone else is using the center of the "empty" case. Which raises the question, did the crew that placed the mon get it "wrong" and the guy with the notes for the straddles and where to put the mon case got it "right" ? I'll have to get a picture, there is some creative concrete seam joinery around the case.
I went back this week and using the same control point for the base, found I was missing everything tied in the area by .3-.4' in a north/south direction. First inclination was that our control point had been disturbed. A lengthy static session showed it to be stable with very little discrepancy from past sessions. So what gives?
Speaking as a geologist, liquefaction may be the cause of the 0.3 to 0.4 ft. shift you recently observed. If I were a betting man, I'd say that the control point was not set in the soup with the other points. If that is true, its position would be less likely to be affected by liquefaction caused by an earthquake.
As a land surveyor, I'd make a distinction in this case that the monuments may have moved, but not necessarily the corners. In other words, it depends! 🙂
Only when I kick the rebar to fit the s/o shot.