CompuServe Messages

Hi … I meant to reply earlier, but got busy! I wanted to clarify what I meant about "backwashing" quakes waves. The first thing I should explain is that I am not a geologist. I am a business woman and musician, not even remotely any kind of scientist. However, one of the things I do in my work is that I am sent on research missions for anything and everything my bosses want to know something about. And when they wanted to buy some property on the West Coast, they decided before they purchased anything they should probably find out as much as possible about the whole area to see where they should live. Fourteen books on geophysics and plate tectonics later, I was talking to the director of emergency management for a major California city. I won't mention his name for the simple reason that HIS superiors would kill HIM if they knew he talked to me. We talked often. This was around the time of the Northridge Quake, so we were talking a lot about that. But we were also talking about the Loma Prieta earthquake and some of the things that they discovered from it. One of the expected things was that the quake waves travelled in soft sand and landfill much faster than in other densities of soil/rock. That's expected. You build your house on sand, and God knows what will happen. In fact, I think he/she issued a warning about that. Anyhow, quakes waves run down soft, loose soil like fire runs down a line of gasoline. You don't want to be there when it happens. With Loma Prieta, one of the things that surprised them is that the earthquake waves seemed to act like water. They literally took the path of least resistance. For example, there is a HUGE solid granite boulder hidden mostly in the ground south of the Bay Area. The township on the south side the form was damaged. The township on the north side of it was, too, but there was no damage in between. And they hypothesized that earthquakes waves of all four forms — primary, secondary, Rayleigh and love waves — ran UNDERNEATH the boulder, and surfaced on the other side, taking the path of least resistance. It kind of sounds like the "aim" or "focus" of waves you were talking about. In the Northridge quake of 1972 — which is, unhappily, a very vivid memory for me since I lived a MILE from the epicenter — had something similar happen, actually. The waves travelled down the San Fernando Valley, encountering mountains on all sides until they came to the Cajuenga Pass, which connects the San Fernando Valley with LA. The waves, sliding on the inside of the "bowl" converged into the pass and ran into LA. There was serious damage in Northridge, and serious damage at the portion of LA that lay at the bottom of the Cajuenga Pass. There is some hypothesizing going on out there with people who actually know what they're doing (and are nice enough to talk to me every once in a while) that says that earthquakes waves act like water in the bathtub. When fast-moving waves of these frequencies encounter dense matter, some of the wave-forms will be absorbed by the matter, and some will echo backward, like sound waves hitting a wall. That's one of my latest current hairbrain theories about why it's so bad in Kobe. The waveforms ran across the seafloor from Awiji Island into the soft sand and landfill of Kobe. Maybe what happened when the waves hit the mountains is that some of the energy was volleyed back, only to meet other oncoming waves of energy. If that is true (big IF!) then it would have complicated things very serious, creating huge standing waves or vertical upshots of energy. Another interesting little tip came from Nightline the other night when they reported that there had been a 10-foot drop in the height of the land at the port itself. Now that's real similar to what happened at Seward, Alaska, when they had their 8.3 a few years back. They had terrible subsidence there. Aerial photographs of it will just scare the daylights out of you. If there were a 10-foot subsidence (literally, a sliding of sandy seafloor off the shelf, resulting in a collapse of the land) at Kobe Harbor, that ALONE would cause an immense, immense series of waveforms to add to the problems they already had. What I am searching for here is why a 6.8 earthquake that happened in Kobe is so much worse than the quake in Northridge, which had a really violent ground motion — more than the REAL scientists thought it should — and so much worse than Loma Prieta, which I think was around the same moment magnitude. And right now my mind seems to be thinking that there is something in the landform there which compounded the intensity of waves. So that is the source of my "pretty funky" comment! I can always be counted on for a few pretty funky comments here and there. It seems to be part of my nature, for good or ill. May liquefaction never real its ugly head in your reality. May it all be fun … Morgaan