Got one more book to finish along the lines of theology before shifting genres a bit. I have given up on only a couple of books in my life, well, other than text books. Many text books I never planned to read all the way through, just enough to pass the tests. And speaking of tests and schools, I had an intense dream last night about a building and a campus I worked in and on many years ago. The building is White Hall and it is located on the southern most edge of the WVU campus in Morgantown, WV.It was at the time home to the College of Mineral and Energy Resources which awarded Bachelors, Masters and Doctorate degrees in Mining Engineering and Petroleum Engineering. The building also housed the departments of Geology and Geography which belonged to the College of Arts and Sciences.
White hall was one of the grandest old ladies on the campus, and just this past couple of years under went a complete rebuild on the interior. I wrote to the project manager at WVU a while ago after seeing an article about the renovation. He invited me down to see the building. They saved all of the Travertine stone work and brass, lots of brass, and marble on the interior. I worked in White Hall on the ground floor for just over 7 years. The entire time I was based in Room 13. Under the ground floor was a full basement with a large room at basement level on each end of the building. The rooms were the entire depth of the building front to back, and rose to about the second floor of the building, which was 4 floors up. The building was 6 floors in total labeled Basement, Ground and 1 through 4. I don't remember if there was enclosed space above the 4th floor or not.
In the basement I was in charge of a room about 10 feet by 10 feet with a notch cut into one corner which enclosed a light trap. In this little room was a seismograph machine which recorded the earth's motion on 3 seismographs using photo sensitive paper. Three graphs because all seismographs record movement as North and South, East and West and Up and Down. Because the paper was light sensitive, changing the records had to be done partly in the red glow of a darkroom light. I maintain that machine for perhaps 4 or 5 years, changing the paper every morning of the year, for 6 years, and developing the prints every few days in a darkroom on the 2nd floor, 4 floors up.
At some point along the way we changed out the photo sensitive paper for plain paper and ink pens for the records. That simplified my life because it did away with working under the glow of a darkroom light twice in the process, and took out the development process altogether. Once the records were changed each day all I had to do was go through them and record my findings to be reported to the National Oceanic and Atmospheric Administration in Fort Collins, Colorado. Most days there were no anomalies to be recorded. The machines were so sensitive the majority of the records were filled with the constant frequency and amplitude compression waves which were the effects of the waves hitting the eastern US seacoast on the Atlantic.
I studied those waveforms for an entire semester before bringing in a geophysics professor and he recognized them immediately and encouraged me to prove him wrong. I couldn't, of course, and had to laugh at all of the time I tried to relate the waves to weather patterns. One of the reasons I was on the weather pattern was because of a geography professor who suggested it might be related to air pressure.
Now if you are wondering about the sensitivity of these instruments, the waves hit the shore at the nearest point to Morgantown WV at something short of 400 miles. Think about how gentle those waves feel on your feet as you relax at the waters edge. That energy travels nearly 400 miles through the rock below our feet, beneath the Piedmont of Virginia, the Blue ridge and Allegheny mountains of Virginia and West Virginia.
To be more honest, it isn't the surface waves that get transmitted, as I explain in a bit, because sand can't transmit motion. It is the wave action deep off the Continental Shelf of the Atlantic where rock transmits the energy back across the land mass.
The sensitivity of those graphs was such that if a truck, or very heavy vehicle of some kind went by on the street outside with a rock in it's tire tread the machine would pick it up. I learned to recognize those quickly.
The absolute coolest thing I ever found on the records was the destruction of the old iron bridge over the Monongahela River between Morgantown and a suburb called Star City. The bridge was replaced by a long span concrete bridge after the iron bridge was found to be nearing it's life span, no pun intended. Because the river was, and is, a main route for coal barges and coal was king in the area the Corp of Engineers and the overseers of river traffic determined the river traffic could only be shut down for part of a day. The old iron bridge had to be cut down and removed between daylight and dusk on a single day.
A crew came in and built enormous wooden boxes around the bridge deck and the supporting iron arch on both ends of the bridge. They filled the boxes with explosives and blew the bridge down in a matter of perhaps 5 to 8 seconds.
Then a tug boat pushing a large barge with a crane came alongside the bridge resting on the bottom of the fairly shallow river, picked it up, turned it 90 degrees so it was aligned with the river, and set the bridge on another barge. And the bridge took leave of Morgantown where it had served very faithfully for many decades.
This was after the seismograph lab had been converted to pin recorders, so I pulled the records an hour or so after the blast so I could find the event on the graphs.
Well, I was stumped a bit. In fact, my mentor, a petroleum professor who had recruited me for the job and trained me in all things seismic was stumped. I can remember Mr. Laird scratching his head and asking me if I had calculated the time correctly. I showed him my calculations based on time and he peered at the seismographs a while. Then a big smile came across his face and he looked at me with this twinkle in his eyes and wouldn't say anything for a long while. Well, a minute maybe.
He sat down beside me and locked his eyes on mine and said, “Let's think for a moment about what happened.”
What had happened and what the seismographs had recorded won me a live spot on the local radio station in the next hour. It was so cool I remember it like it was yesterday.
The bridge structure was cut by 4 large blasts of an explosive of some kind packed in sand. Explosives always give off high compression energy. Which is why I, we, were looking for a large compression wave at the exact moment of blast. Remember these instruments could record a rock in a tire of a truck going by. But the boxes didn't contain just explosives. The also contained SAND. Sand is the worlds best natural energy absorber. If you want to earthquake proof a structure, float it in sand. The world famous Tokyo Hotel suffered several earthquakes and finally burned down after surviving World War II because of an earthquake. The owners rebuilt the hotel even grander than before but floated the entire building in a bed of sand. The hotel never again suffered any damage from an earthquake. Sand can not transmit motion. It is impossible.
So when the explosives produced thousands of tons of force shearing the roadbed and the iron arch braces, the force was absorbed in the sand and the little bit of compressive force left over was quickly dissipated into the air. Air can transfer force more faithfully than sand, but not much more.
So the result was no compression wave was pushed into the earth, no major compression wave recorded. What a let down. But wait, the story isn't over.
The piers upon which the bridge rested had for decades been pushing on the earth in which they were resting. When the bridge weight was instantaneously removed from the piers the piers rebounded. The pressure holding them down was suddenly released and they moved up, opposite of the the decades load, and produced not a compression wave, but a dilatation wave. And we DID see that at precisely the moment of blast. In fact it was the dilatation wave that had us so confused. Why was the geology beneath the seismograph pier moving away? It was because the piers were able to relax, for only part of a second, but definitely relax from the weight it had withstood for decades.
And that was the coolest day in my short 6 years of running the seismograph lab.
Just thought I'd share. Hope you enjoyed a short lesson in geophysics.