European Salon de News, Discussion et Klatsch – 8 January | 121 comments (121 topical, editorial, 0 hidden)

Re: This, That, and the Other (none / 1)

Swissinfo: Geothermal project shakes Basel again

Basel has been rocked by another earth tremor, this time measuring 3.1 on the Richter scale, that centred on the site of a planned geothermal power plant.
This time buildings stood up to the force unlike the minor damage inflicted by a small earthquake in December that clocked a reading of 3.4. Nobody was hurt in either of the two incidents.
The latest tremor took place at 08.19 on Saturday, prompting around 40 residents to call the emergency services.
Work on the Deep Heat Mining project stopped last month following a series of tremors and will not resume until at least the end of January when experts are expected to conclude their analysis.
The project plans to plans to recover heat to generate electricity by pumping water deep into the Earth's crust.
The injection of water into rocks five kilometres below the surface began at the start of December last year, but only lasted a few days. Since the process started more than 100 small tremors have been recorded. Basel has been rocked by another earth tremor, this time measuring 3.1 on the Richter scale, that centred on the site of a planned geothermal power plant.

by Fran on Mon Jan 8th, 2007 at 12:19:32 AM EST
[ Parent ]

Re: This, That, and the Other (none / 1)

I have mixed feelings about this project. It is good to have alternative energy, on the other hand it is not so funny when all of sudden everything starts moving while talking on the phone, as happend in December. Considering the history of the city and that it is already siting on an seismic active area I just don't know what to make of this.

by Fran on Mon Jan 8th, 2007 at 12:36:19 AM EST
[ Parent ]

Seismics (none / 1)

I understand your ambiguity. And now the inevitable word you probably would be expecting the moment you saw I've responded:

But:

Consider that water is the ultimate lubricator for the earth's equivalent of having sex. Which is after all what the Alps represent: the ultimate hump although with little penetration, that is, subduction so far.

Cough. Okay. Back zo zhee lesson!

Tremors up to 3.5 or even 4 on the Richter scale are quite common for pumping experiments (also in oil and gas), considering the pressures in use. The earth's crust is adapting and settling to newly inserted pressures - but which are relatively minor to the forces active all the time. It's like a wooden house whose rafters and roof are settling to the new distribution.

On the question whether increased pressurized water into the crust would result into increased earthquake activity, I'd have to say yes - which is a cop-out, because it's already happening. But whether it would lead to more severe earthquakes, I'd stake real money on No. There's even a chance that exactly because of the presence of more water down there it will actually lower any -natural- amount of severe earthquakes - which would come to the expression of a series of less severe quakes. But if the genesis of earthquakes is deeper than the 5 km - all best are off.

Having said that, there have occurred a limited number of unpredicted accidents on geothermal projects - but those were dominantly blow-outs in volcanic areas.

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 06:42:34 AM EST
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Re: Seismics (none / 0)

I am not a geologist not do I play one on TV, but if I am not mistaken an increased number of small tremors due to improved lubrication by water would reduce, not increase, the chance of large earthquakes.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 06:47:44 AM EST
[ Parent ]

How so? (none / 1)

Could you lay the trail of logical breadcrumbs for me on this?

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 06:53:07 AM EST
[ Parent ]

Re: How so? (none / 0)

O-kay...

Scream when I say something stupid.

Here's my mental model of earthquakes...

At geological faults one has two pieces of the earth's crust moving relative to each other while in contact. This is like grinding two slabs of rock against each other at high pressure. If the two slabs are very coarse (as tectonic plates are) some of the irregularities will get locked to each other and resist motion, until the accumulated stresses are large enough to break the obstacles. Then an earthquake happens and a large relative motion occurs in a small period of time. The point where the surface irregularities caused the locking and which ultimately broke is the epicentre.

And here's my reasoning...

I reason that improved lubrication will allow the two plates to slide more easily. If you measure the average relative speed along the fault it will be the same, but instead of a few large lurches with long periods of quiescence, with improved lubrication the displacement will happen in more frequent but smaller jumps.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 07:01:57 AM EST
[ Parent ]

Re: How so? (none / 0)

Just for fun: Plate tectonics animations...

by the stormy present (stormypresent aaaaaaat gmail etc) on Mon Jan 8th, 2007 at 07:17:06 AM EST
[ Parent ]

You're doing (4.00 / 2)

superb on the mental model - but you can just as well leave out irregularities. Surely they may contribute, but are probably not conditional. The idea of irregulartities is common - it stems from the Discovery Channel et al cartoon simplification to visualise the lockdown of plates. Lies to children.

One more slight correction:

The point where the surface irregularities caused the locking and which ultimately broke is the epicentre.

An epicentre is indeed the estimated point of origin of the stress release and 3-D displacement. Yet it does not necessarily imply it's also the place where the locking was caused initially. It is possible, but it doesn't need to be. It's a big plate.

Separate post for the reasoning...

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 07:19:37 AM EST
[ Parent ]

No screaming yet (none / 1)

I reason that improved lubrication will allow the two plates to slide more easily.

Agreed.

If you measure the average relative speed along the fault it will be the same, but instead of a few large lurches with long periods of quiescence, with improved lubrication the displacement will happen in more frequent but smaller jumps.

I think the word to focus on here is "large". I just read your initial comment as well, it also contains "large earthquakes". We'll need to define large - because I still don't see how from this line of reasoning you can imply there will be more severe earthquakes... Because smaller jumps imply to me that at lower stresses an earthquake can be triggered.

Picking up on TSP's comment, we need to split up large in 1) amount of energy released (eg., the seismic moment) 2)level of total displacement and 3) the magnitude of amplitude. They're all interconnected, but I think the metric used needs to be straightened out first. Energy is most probably the least complicated for now.

But first I'm going to do something terribly annoying. I'm going back to work. Back here at six-ish.

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 07:53:49 AM EST
[ Parent ]

Re: No screaming yet (none / 0)

Let's focus on the assumption that the average shear speed of shear along a fault is independent of the local conditions and is more determined by the bulk motion of the plates themselves.

Assuming that doesn't make you scream, what do things look like if the same average displacement is achieved with one earthquake per century as opposed to one per year?

I claim that injecting water cannot increase the long-term average shear speed, but only the number of individual jumps. This makes each individual jump smaller.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 08:01:37 AM EST
[ Parent ]

Re: No screaming yet (none / 1)

Are you two agreeing or disagreeing with each other?

by Colman (colman at eurotrib.com) on Mon Jan 8th, 2007 at 08:03:21 AM EST
[ Parent ]

Re: No screaming yet (none / 0)

I think we're not disagreeing.

If I manage to extract a strong disagreement from the resident geologist I'll stop ;-)

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 08:04:40 AM EST
[ Parent ]

Delayed but (none / 0)

full of vigour and food.

I claim that injecting water cannot increase the long-term average shear speed, but only the number of individual jumps. This makes each individual jump smaller.

And that's fine with me.

But this:

what do things look like if the same average displacement is achieved with one earthquake per century as opposed to one per year?

Makes my tires go screech. As you assumed (correctly) that the push rate of the plate is constant, resulting into a displacement of x after 100 years, what does this imply? If you mean that the same displacement x is now reached within 1 year, your push rate flies off the rails. That's a no-go area - also because you expressly stated average motion would stay constant.

Small detour: a lowering of friction -by the addition of a lubricator- does not imply that Fran's cottage will suddenly be pushed northwards -faster- but that the distribution will be more gradual.

Therefore, if you meant that we end up with, say, 50 tiny earthquakes with a mean displacement of x/50 during 100 years, total displacement x is the same. But in that case, your total movement is gradual and distributed of tiny pieces of energy - hence smaller earthquakes.

One caveat: if, in the extremely unfortuitous and remote chance, people start pumping water in a fault that's under extreme pressure, you might visualise that we trigger the big whopper. There is that, I'd say.

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 04:11:09 PM EST
[ Parent ]

Re: Delayed but (none / 1)

Yes, I would have to add to the discussion above that, if according to estimates a large earthquake is long overdue (i.e., displacement along a fault is lagging average desplacement by a long distance) then lubricating anywhere along the fault is probably the wrong thing to do.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Tue Jan 9th, 2007 at 05:26:56 AM EST
[ Parent ]

Re: Delayed but (none / 1)

If you mean that the same displacement x is now reached within 1 year, your push rate flies off the rails. That's a no-go area - also because you expressly stated average motion would stay constant.

Yes, that would be absurd.

Small detour: a lowering of friction -by the addition of a lubricator- does not imply that Fran's cottage will suddenly be pushed northwards -faster- but that the distribution will be more gradual.

Yes, that's what I meant.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Tue Jan 9th, 2007 at 05:29:11 AM EST
[ Parent ]

But but but (none / 0)

then we are in full agreement! How did that happen?

What threw me off was your initial sounding hesitation, voiced in the geologist on tv remark. It took me two re-readings to realise you were saying the exact same thing. But it never hurts to go under the surface, he said wittily.

Time to prepare yourself for your first appearance on Sky News!

by Nomad (Bjinse) on Tue Jan 9th, 2007 at 07:08:53 AM EST
[ Parent ]

Re: But but but (none / 0)

I don't think you really addressed Fran's real fear

Considering the history of the city and that it is already siting on an seismic active area I just don't know what to make of this.

which is a repeat of the 1356 Basel Earthquake. My point is that more frequent magnitude-3 (barely noticeable) earthquakes due to lubrication actually (and counter-intuitively) reduces the chance of a repeat of a magnitude-6 (destructive) earthquake.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Tue Jan 9th, 2007 at 07:22:15 AM EST
[ Parent ]

Re: But but but (none / 0)

And I think that is quite a big claim that warrants a disclaimer.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Tue Jan 9th, 2007 at 07:24:18 AM EST
[ Parent ]

Perhaps (none / 0)

I'm going dense. Which wouldn't be the first time.

But how is your point:

more frequent magnitude-3 (barely noticeable) earthquakes due to lubrication actually (and counter-intuitively) reduces the chance of a repeat of a magnitude-6 (destructive) earthquake.

different than the one I made:

exactly because of the presence of more water down there it will actually lower any -natural- amount of severe earthquakes - which would come to the expression of a series of less severe quakes.

'Xplain please!

While we're at it - some extra considerations:
This whole thread began with the surmise what would happen IF the water would be pumped into a fault.

we've gone completely past that surmise whether water actually -is- injected into an active fault (which is practically unlikely because a major fault is a particularly bad reservoir rock.)
how that particular fault relates to the stress distributioning within the Alps (is it major? is it under stress duration?)
and perhaps to repeat: that anything which happens below 5 km is beyond any safeguard anyway - which for the crust alone makes up a remaining 90 percent.

by Nomad (Bjinse) on Tue Jan 9th, 2007 at 08:15:34 AM EST
[ Parent ]

Re: Perhaps (none / 0)

Or maybe I'm just belabouring the obvious, which also wouldn't be the first time.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Tue Jan 9th, 2007 at 08:35:21 AM EST
[ Parent ]

Perhaps... (none / 0)

Yet if we lay this to rest like this, it will haunt me for the rest of my life... Pondering in my rocking chair the days of yore, "That Mig chap and his earthquakes... My, my... what was that about...?"

by Nomad (Bjinse) on Tue Jan 9th, 2007 at 07:04:21 PM EST
[ Parent ]

Re: Seismics (none / 0)

I found this cool site: Induced Earthquake Bibliography with the following warning:

The very fact that someone has studied the possibility of induced seismicity at a given site or related to a given activity does not mean that that activity or site has really induced seismicity. It certainly does not mean that the activity has "caused damaging earthquakes." Some human activities do cause damaging earthquakes but most induced seismicity is not damaging. You really need to read the journal articles in the bibliography to understand the results of the studies. The newspaper and magazine articles listed are (as usual) to be taken with a few grains of salt. Reporters often don't understand the science and publish errors.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 06:54:05 AM EST
[ Parent ]

Re: Seismics (none / 0)

I was under the impression that the Richter scale is no longer the standard for measuring earthquake magnitude, having been largely supplanted by the moment magnitude scale?

by the stormy present (stormypresent aaaaaaat gmail etc) on Mon Jan 8th, 2007 at 07:13:34 AM EST
[ Parent ]

What have I done... (none / 1)

Nothing is mere. Migeru, I may need to steal your former sig-line to keep me reminded.

You're correct. The Richter scale remains useful, however, for direct analysis and (for instance) tsunami warnings. Richter is the metric for amplitude magnitude.
Hence it was a lumbersome metric which did not incorporate several elements of an earthquake, such as the level of displacement along the fault - and far more brilliant people have attempted to come up with a better one. The moment magnitude scale has become increasingly the standard during my education.

The big plus: it estimates the amount of energy that is released during an eathquake.

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 07:29:46 AM EST
[ Parent ]

Re: What have I done... (none / 0)

Another big plus if you're writing in the press: people know the Richter scale, and have an intuition of past historical earthquakes with particular values onthe scale. Talk about "moment magnitude scale" and people will go 'huh?'?

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 07:34:40 AM EST
[ Parent ]

Re: What have I done... (none / 0)

I'm actually surprised to hear you say that, since scientists are famous for complaining that journalists "don't understand science" and therefore get their facts wrong. (Which I think was actually done elsewhere in this thread....)

It simply isn't accurate to say something is being measured on the Richter scale if it's not actually being measured on the Richter scale. It actually bugs me quite a lot to see the press refer to the Richter scale, since I was taught many years ago that it is not the standard measure. Better to just say "magnitue" and leave it at that, e.g. "an earthquake of 7.6 magnitude struck such-and-such...."

by the stormy present (stormypresent aaaaaaat gmail etc) on Mon Jan 8th, 2007 at 07:46:07 AM EST
[ Parent ]

Re: What have I done... (none / 1)

But the two "magnitudes" measure different things.

The Richter magnitude test scale (or more correctly local magnitude ML scale) assigns a single number to quantify the size of an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a seismometer output. Measurements have no limits and can be either positive or negative.

The moment magnitude scale was introduced in 1979 by Tom Hanks and Hiroo Kanamori as a successor to the Richter scale and is used by seismologists to compare the energy released by earthquakes. The moment magnitude [...] is a dimensionless number defined [in terms of the seismic moment]

Seismic moment is a quantity used by earthquake seismologists to measure the amount of energy released by an earthquake. The scalar seismic moment M0 is defined by the equation M0 = μAu, where

μ is the shear modulus of the rocks involved in the earthquake, typically 30 gigapascals[1]

A is the area of the rupture along the geologic fault where the earthquake occurred, and

u is the average displacement along the fault

Despite

The major problem with Richter magnitude is that it is not easily related to physical characteristics of the earthquake source. Furthermore, there is a saturation effect near 8.3-8.5, owing to the scaling law of earthquake spectra, that causes traditional magnitude methods (such as MS) to yield the same magnitude estimate for events that are clearly of different size. By the beginning of the 21st century, most seismologists considered the traditional magnitude scales to be largely obsolete, being replaced by a more physically meaningful measurement called the seismic moment which is more directly relatable to the physical parameters, such as the dimension of the earthquake rupture, and the energy released from the earthquake.

doesn't the definition of the Richter scale imply it's more relevant to what the earthquake felt like in the vicinity of the seismogram? In addition

In 1979 seismologists Tom Hanks and Hiroo Kanamori, also of the California Institute of Technology, proposed the moment magnitude scale (MW), which provides a way of expressing seismic moments in a form that can be approximately related to traditional seismic magnitude measurements.

indicates that the point is partially to be able to reduce things to a sibgle number so they can be ranked.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 07:56:54 AM EST
[ Parent ]

Re: What have I done... (none / 0)

I mean "the vicinity of the seismograph". That is, where people live.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 08:02:43 AM EST
[ Parent ]

Re: What have I done... (4.00 / 2)

I know they measure different things. I also know what they measure. Which is why I object to seeing press articles stating that an earthquake measured such-and-such on the Richter scale when in fact, the given number actually represents moment magnitude.

I have no problem with seismologists measuring earthquakes on the Richter scale if they choose to do so; I am not a seismologist, and that's their business. But since most of the commonly reported magnitudes are not measured on the Richter scale, it is inaccurate to continue slapping the Richter label on a different kind of measurement.

The USGS Earthquake Hazard program, which tracks seismic activity around the world, refers simply to "magnitude," which is both simple enough for laypeople and still accurate.

by the stormy present (stormypresent aaaaaaat gmail etc) on Mon Jan 8th, 2007 at 08:08:15 AM EST
[ Parent ]

Re: What have I done... (none / 0)

Ah, ok, I see your point now.

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 08:20:01 AM EST
[ Parent ]

Yes well (none / 1)

There are too few Buddhists around in the public to know that the one constant in life is change.

Besides, seismologists also measure the Richter scale. It's not that scientists are lying...

Not all of the time, anyway.

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 08:00:42 AM EST
[ Parent ]

Re: Yes well (none / 0)

I didn't say the scientists were lying!

But if I go here and look up an earthquake, for example this one, its stated magnitude is probably not a Richter magnitude.

by the stormy present (stormypresent aaaaaaat gmail etc) on Mon Jan 8th, 2007 at 08:12:11 AM EST
[ Parent ]

Re: Yes well (none / 0)

If you click on the hyperlinked "Great" next to the magnitude quoted, and scroll up, you'll see that they have 5 different definitions of magnitude, and that they don't tell you which one they mean. Well, they do: in the original page they say "M-type=teleseismic moment magnitude (Mw)" under "parameters".

Those whom the Gods wish to destroy They first make mad. -- Euripides

by Carrie (migeru at eurotrib dot com) on Mon Jan 8th, 2007 at 08:18:38 AM EST
[ Parent ]

Re: Yes well (4.00 / 2)

Yes, and this one is body magnitude (Mb), and this one is local magnitude (ML), which is actually a Richter (or Richteresque) measurement.

All the more reason to just say "magnitude."

by the stormy present (stormypresent aaaaaaat gmail etc) on Mon Jan 8th, 2007 at 08:48:03 AM EST
[ Parent ]

Re: Seismics (4.00 / 3)

So, basically you and Migeru are telling me that next time my room shakes because the are pumping water in the earth again - I just have to think that they are lubricating to ease seismic earth sex for tension release. Wow - what a concept, guess will be a whole new experience. :-D

by Fran on Mon Jan 8th, 2007 at 09:33:08 AM EST
[ Parent ]

Exactly!! (none / 1)

Which is why geoscientists often have T-shirts bearing the text: "the deeper you go, the hotter it gets."

by Nomad (Bjinse) on Mon Jan 8th, 2007 at 04:12:51 PM EST
[ Parent ]

European Salon de News, Discussion et Klatsch – 8 January | 121 comments (121 topical, 0 editorial, 0 hidden)

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