Fault geology of Hamilton, Ontario

As I have mentioned previously, one really huge fault whips down through Toronto and Hamilton. Now it happens in my many travels and fishing trips, that the most dramatic scenery is associated with earthquakes. If you take the beautiful seacoast road down from San Francisco, you can see these marvelous terraced beaches. Each terrace has been created by a huge M9 earthquake! If we didn't have earthquakes, everything would be ground to a pulp, and be as boring as Toronto!

This fault appears to be most active at Hamilton, and the spectacular topography is a result.

Good old Hamiton is located at the west end of Lake Ontario. It is noted for its stinky steel mills, and less noted for the swamps everywhere. In fact, I was told these swamps are extremely deep, and have blocked decent railroad access for years.

I have been playing around with Digital Elevation Models (DEM's), and viewers. I was using 3DEM to great success. Here a shaded relief view of Hamilton.


That great big gash in the Niagara Escarpment is the Dundas Valley, which was also a major glacial lake drainage outlet, and affects the sediments in Lake Ontario for a great distance. Nobody has really wondered why it is there.

The real fun with 3DEM is taking oblique views. Here's one, shooting down the fault.


Now, don't you wonder about Hamilton? The view would be much more spectacular if we could remove the sediments. Then you would see something! We did a lot of geophysics out in the lake, where you can get an idea of the depths of the swamps.

Why do we even care about Hamilton? First off, the scenery is nice. Second, all those swamps are formed by an active fault, somewhat like sag ponds, but over a much longer time. They are doing a lot of building in those ponds, and I think it is somewhat dangerous.

The next big earthquake in that area will be a high-speed thrust, much like some of the more destructive earthquakes that hit Japan recently. The damage intensity will have a very narrow zone with a high Peak Ground Velocity (PGV). The deep swamps will amplify this ground motion 10 to 100 times. The damage will be incredible! This earthquake will blow out the electricity and natural gas for most of Southern Ontario.

Yet, we merrily go on, ignoring this threat, not doing the slightest little thing to mitigate the disaster. Such is the power of living memory! We remember Hurricane Hazel, because it happened, yet this earthquake has the same general odds of happening. Just hope your house is on solid ground!

Fault mechanisms boring story - II

If you recall, I left you asleep at the point of wonder why we have earthquakes at all in Eastern North America (ENA). Really, if the continent is one big massive piece of tombstone granite, then any stress-relieving earthquake should just carve a 'stress-hole' like boring a mine.

Once this giant Tim Hortons donut gets formed, the remaining rock arches around it, and leaves a perfectly stable structure, with an extinct fault in the middle. This doesn't happen on the plate margins, with all those plates sliding past each other, like those sliding number puzzles we had as kids. For the equivalent, we would need mountain ranges or visible fault sliding to keep the similar ENA earthquake hotspots going for a few million years.

Take a typical fault zone trying to grow up in ENA. It starts with a fractured weak spot, perhaps reactivated by the modern stress field. Eventually (perhaps), the shear stress builds up along a fracture, and the bath-tub feet let go! The fractured rock behaves exactly the same as in California or Peru.

But that's it! Our poor little earthquake has shot its load. The feet have lost their stress, and the surrounding rock has clamped up on our poor little fellow. He can't grow up...

That is, if our earthquake follows conventional thinking for ENA earthquakes. But no, our earthquake fault zone is smarter than that, it is following Harold's original thinking, which doesn't get into the university cartel, because they all got tenure!

Once our earthquake has caused its bump (like a Utah coalmine!), it looks around and sees what it has done, which is to freshly fracture a lot more rock. Its seismic effort hasn't gone into mountain building, or plate sliding, it's gone into fracture surface energy! The academics never thought of that!

But this isn't enough for Quakey (like that name?), in its battle against the implacable rock. Luckily, he's (she's?) under a big hunk of water, and water slowly flows into the new fractures. Now things are cooking! The water does all sorts of wonderful things. First, the water pressure reduces the normal stress on the faults and makes them more likely to slide again. Second, the water hydrofractures and extends existing tension cracks. Finally, the fresh water is corrosive and starts chewing at the adhesion points.

Quakey has become a growing entity, like the Blob that ate New York. So, under Hamilton, New Madrid, countless other ENA locations, we have growing things, which although not actually alive, can give a darn good account of themselves!

As Quakey grows, he can tap into more stress from the surrounding rock, just like we were excavating a new Utah coal mine (or an underground nuclear waste thingie!). He gives many signs of his growth, lots of little earthquakes, just like his bigger plate margin brothers. All the bathtub feet are working, and eventually there is a large, scale-limited earthquake. The process begins again for a bigger earthquake!

Quakey may start as a simple thrust fault along a pre-existing fracture, but soon suffers growing pains. The old fracture provides the water, but a simple thrust fault isn't enough to suck out all the stress from the surround rock. In order to avoid another stress lockup, he must start developing shear wings, which produce strike-slip earthquakes. When he eventually grows into a monster, he resembles the New Madrid fault system.

All the time, these zones are sending the signals to prove Harold is right, and the others are wrong, but the scientists and politicians are too cheap to provide the detailed seismic monitoring that is required. Only the Southern Ontario Seismic Network probably has sufficient horsepower and density, but the Hamilton zone is just a baby!

Everyday, these zones try to show themselves. They send typical 'fluid injection' earthquakes, they mix thrust and strike-slip mechanisms, and they only show up under bodies of water. But without monitoring, the world goes on arguing with Harold....

The perfect nuclear plant

I'm about the only nuclear seismic expert who talks. Everybody else works as a consultant and has to be quiet, in order to satisfy political bosses with money. The most exciting thing (recently) in the nuclear seismic business has been a thing called Experience Data. You won't find this on the Internet, but it's a lot of fun! Like fishing!

Basically you start with the idea that all industrial plants are the same to an earthquake. There are transformers, barrels of waste, storage tanks, pipes, etc. Then, the seismic fishermen go around to all areas that have had earthquakes, and look at the industrial plants. They look for damage, and especially non-damage (which most people don't look for!). They compile tables (a lot of data!), and determine what gets damaged the most, and what never gets damaged.

This information has completely turned a lot of conventional seismic engineering on its head. There are many things that get damaged which the old engineers ignored (like Japan!). There are things that never get damaged, which engineers pour billions into (like pipes!). Old OPG is spending billions (more or less) in replacing feeder pipes which can absolutely never get damaged in an earthquake. It's all due to the old crap analysis which I'm sure the Japanese love (and OPG!).

The Japanese had a lot of experience data from previous earthquakes. But like The Claptrap Society, they never talked about it, or participated, as long as they could keep quiet about it. As far as we knew, they never applied the findings to their own plants (quiet again!). In Experience Data, there is some really, really good information on seismic interaction. Of course I would never say 'never, never' because of Conrad Blackism Libel Chill (I'm just kidding everybody!).

And so this brings us to our new nuclear plant in Ontario (and a very long post!). Are we applying the old crap or the new stuff? I'm not very hopeful, because so far, everything has been very politically correct, trying to keep everybody happy. There is no hope we can build a new nuclear plant, when we really need it to keep on my air conditioner in the Home.

Here's how to bring it on-line in my lifetime. Forget all the PC crap. Just lay down the only design that can be built by 2014, and people can take it, all or nothing. Of course, I know the only thing that can be done in that time, and I'll save it for another post. Right now, they are jamming 4 reactors sideways, in a postage stamp lot, with damn cooling towers, that will cast a permanent ice fog on the 401 and kill everybody! Does anybody think this can be built?

Catching a Whopper

As mentioned earlier in Seismic Fishing, we found the grand-daddy of all data fishing holes, in the tape vaults of Texas. Besides nailing down the deep crustal structure of Ontario, we found the biggest fish of all: a giant Precambrian clastic basin right under Lake Erie!

Lake Erie was always a weird lake for us. It's very shallow, and during a cold winter (which we don't get anymore!), it can freeze right over. Once, we wanted to put in a giant underwater power cable to the States. We eventually found out that the winter ice smashes together like plate-tectonic subduction and forms giant pressure ridges, which can gouge huge trenches in the lake mud. That would mean the cable would have to be deeply buried (too expensive!), even though all those natural gas well-heads also keep getting ripped out (but nobody talks about that!). As well, the cables would have to be DC, and we couldn't find conductive earth for a grounding mat in case of a cable break. Without good grounding, a DC cable fault would turn every cow in the region into instant hamburger!

Enough old-man digression! It is generally assumed by the Paleozoic people (including oil and gas types), that the Precambrian granites (metamorphics), are flat-lying, featureless, and solid (like a rock!). The basement rock forms a solid plate for the pancake sedimentary layers, and has nothing to do with the location of oil, gas, and earthquakes. Our discovery shocked them, and they rushed to drill at the new targets.

The paper for today is "Seismic images of a tectonic subdivision of the Grenville Orogen beneath Lakes Ontario and Erie". Available behind the paywall.

This is the index map of the paper. We are only considering the little piece in the box, although there is a ton more data around the rest of the lakes. Note the tentative location of the other two sisters. The Grenville front is waaaay out in Lake Huron which will make the DGT panel happy. Sister #1 (Elzevir) conveniently stops at the limestones, but this paper shows that Sister #2 has a merry old time crashing right through!

Here's the seismic section.

The section shows what a mess it makes of the Paleozoic. The box marked II is the basin, which is quite large! At least the oil companies knew it was a drilling target, they don't make the 'pancake' assumption. The paper goes on to recontruct how this could happen, mainly by having a giant mountain ranges, which then collapses under its own weight.

And that's all she wrote...

Cornwall Earthquake 1944

I'm enjoying my post-work sabbatical. Unfortunately, I couldn't get to the dock this weekend because of teenager commitments, my daughter is off to Prague to represent Ontario in water polo! Yeah Ontario!

One advantage of being old is that you have gathered a lot of old stuff that somehow is missed by the modern Google data vacuum. I have an obscure copy of "A geological study of the Massena-Cornwall earthquake of Sept. 5, 1944, and its bearing on the proposed St. Lawrence River project", by Charles P. Berkey, Geologist, New York, April 10, 1945.

This was one of the more fascinating books of my career, when I first read it. My in-laws were living in Cornwall at that time, so I also talked to them about it. For emergency planning purposes, I considered this the perfect model for the likely Toronto earthquake (following the numbers!). It's magnitude is uncertain (especially on the countless magnitude scales!), but is somewhere between 5.5 and 6.0. Again, nobody in soundbite-land will acknowledge the hazard, but we are as likely to experience this type of earthquake as most anywhere else in eastern North America (ENA).

"The earthquake began with a violent shock accompanied by terrifying noises, including sounds and loud rumblings, at 12:38 am Sept. 5, 1944. This was followed by a second shock later in the same morning, with many aftershocks and tremors of minor character distributed through the following days." "According to these observers, the estimate of a million dollars damage for each of the larger villages, is probably not too high. It is made up almost entirely of small items affecting perhaps 90% of buildings in the town. ... practically every one of the 3081 homes and buildings was damaged, although only a few to a serious extent."



Of course, all the damage was on the soft soils by the river, which consists mostly of the notorious Leda Clay. There were numerous liquefaction events. Up on the hard tills, the earthquake was hardly noticed (from my in-laws!). From my experience, I estimate that the Peak Ground Velocity (PGV) was about 500 mm/sec on the soft junk, and about 5 mm/sec on the hard tills and rock, an amplification factor of about 100 times.



If we transpose this earthquake to modern Hamilton (the most likely location), we would probably get about 0.1 to 1 billion dollars in damage and economic disruption. I would suggest that the teeniest bit of special planning would reduce this by 10's of millions of dollars. The numbers show the odds at about 1% chance per year, so this gives a present value of about a million per year, which we should be spending.

Swamp Gas

With all my canoe tripping, the thing I like most doing is gliding through a swamp. There's something about these fantastic carbon sinks that goes back into ancient geology. You dip the paddle, and glorious methane bubbles up. The biggest fish are also in the swamp, the really large largemouth squeeze into impossibly shallow water, just to get a chance at those millions of frogs!

When I first entered the workforce, I got hold of this almost magical (like Harry Potter!) map. It was an old topo sheet, but it showed the old gas seeps, and farmer wells in the area. You know that there were no big companies drilling here. Most likely, farmers noticed the killed vegetation, and the bubbles, and sunk in a pipe to light the farm. I scanned part of the map here.

You can see (Click on it!) all the gas wells around Binbrook, the heart of darkness (for major seismicity) in this area. When gas bubbles up, it means that fluids are moving deep in the earth, and this is significant for earthquakes. You don't see this gas towards Niagara Falls. In fact, we blasted two huge tunnels (and another on the way!) without encountering any gas. In the lake, the geophysics shows plenty of gas 'pockmarks' where the gas has blasted the soft 'loonshit'. No gas in Toronto, where this megafault hanging wall runs through the city, mainly because the sediments get thin, and not too much in the way of gas-generating oily shale. We did encounter some gas in a borehole at the old Lakeview generating station, and it nearly blew somebody's head off when he snapped off the cap!

The presence or absence of gas and oil is an indication of the general openness of the rock (permeability). You're not getting any gas through my magnificent rock up on the north shore of the lake! Another story will tell my musings on the causes and how deep fluid flow is the ultimate driving force, projecting a fairly significant earthquake threat (seismic hazard ) to the whole Golden Horseshoe.

Force of Nature

There's nothing like the force of a largemouth bass hitting your feeble little fishing line. I keep the drag on light, and hope to tire it out before it breaks my line. When I'm camping with a bunch of fish-hungry teenagers, we'll eat the bass. But I remember once on Georgian Bay, when I caught a huge fish. I was ready to fight it, when the darn thing zoomed right under my canoe, snagged my line, and lept like a daemon, breaking the line. I always considered Georgian Bay to be a place of large mysteries.

Today, I'm celebrating another Georgian Bay mystery, with an earthquake right where I expect a seismicity pattern will fill in.

You can read all about this earthquake on the SOSN website. I had a lot of fun helping to put together this seismic network, but that's another story. This 'big fish' is part of a pattern that is filling in for that area.

It's rather amazing that stable patterns didn't fill in for the Hamilton and Lake Ontario regions until we had good seismic monitoring for 15 years. The Bruce area was always considered totally devoid of seismic fish, because nobody was monitoring, and now they are getting caught. Over the next few years, I expect a full Hamilton pattern developing there, which means that it is a water-activated fracture zone on a major Precambrian megathrust, much like Hamilton and Prince Edward County.