Dust flux, Vostok ice core

Dust flux, Vostok ice core
Two dimensional phase space reconstruction of dust flux from the Vostok core over the period 186-4 ka using the time derivative method. Dust flux on the x-axis, rate of change is on the y-axis. From Gipp (2001).

Saturday, May 30, 2015

Earthquakes and oil wells in Oklahoma

Further to last week's post on Oklahoma induced earthquakes, I have taken two slides (nos. 8 and 9) from this presentation (pdf), and plotted one atop the other.


In the above figure, the purple circles represent well completions from June 2010 to 2012 (appearing as a semi-transparent layer overtop the other), and the yellow circles represent the epicentres of earthquakes over the same time frame. Not all wells are associated with earthquakes. Most of the earthquakes are located in a few clusters, the three largest of which have been circled.

The reason that not all fracking (and its associated waste water disposal) causes earthquakes is because the local geology has to be predisposed towards producing earthquakes. There have to be natural stresses within the rocks to be released, and it helps if there are pre-existing faults to be activated by these stresses.


The three largest earthquake clusters plotted on a  geological map of Oklahoma (source - pdf). Interesting and complex structures lie at the root of the eastern portion of the map, as well as across the southern portion.


The three major earthquake clusters plotted on a map of fractures in Oklahoma (slide 14 in this document - pdf). I think the projections were different, which was why I couldn't get a very good overlay. But the lower two clusters of earthquakes are definitely in heavily faulted rocks--the northern cluster less so.

Monday, May 18, 2015

'Fracking' breaks Oklahoma

Well, maybe not yet.

This story in Zerohedge has attracted the interest of the Centre for World Complexity (that's me). So I've decided to take a little break from my ongoing travelogue of China to talk about some real geology for a change (possibly the first time this year).

Our topic today is intraplate earthquakes.But rather than reiterate what Wiki has already collated, let's apply our limited understanding of earthquakes to the situation in Oklahoma, while noting that our conclusions may also be applicable in other areas where fracking is being pursued (North Dakota? Saskatchewan? Ontario?).

Most large earthquakes happen at the edges of tectonic plates where the grind slowly past one another, but there are large stresses within plates as well. For one reason, the continental plates are all composed of small bits of tectonic material that have all become stuck together due to innumerable collisions of smaller pieces of material which couldn't be subducted. Because the plates are so large, the forces that drive them are dispersed over a large area, and stresses accumulate not only near the edges, but along any fracture that may exist within the plates interior.

Sometimes these intraplate stresses cause really big earthquakes. Perhaps the most famous such earthquakes happened in New Madrid, Missouri in the early 19th century. With a magnitude up to 8, they were the largest known earthquakes not directly related to a subduction zone in America's (known) history.


Seismic hazard map for the United States, from here.

Seismic hazard can be assessed in a couple of ways. By far the most significant approach is based on a study of the historical record of earthquakes. Hence, the two big red spots in the eastern US come from the large series of earthquakes in New Madrid in 1811 to 1812, and the Charleston earthquake in 1886. Several earthquakes have also occurred in the St. Lawrence valley (NE US) as well.

The historical record in the US is short, but the geology is long. The scale invariant nature of earthquakes allows us to estimate the recurrence interval of very large earthquakes in other places of the map (devoid of historical large earthquakes). Such recurrence intervals may be greater than a thousand years In such areas, stresses do build, albeit slowly--thus the likelihood of a large earthquake may be much greater than estimated purely on the basis of the historical record because it is so short.

Pumping liquids under pressure deep into the rocks has been correlated with small earthquakes since at least the 1960s. Our understanding of why this happens is more recent. It seems the fluids act much like a lubricant, allowing stresses that are already present in the rocks to be released. As far back as the 1960s, there were proposals for using such methods to control the build-up of stresses in the rocks and so prevent large earthquakes from occurring--however the approach has not, to my knowledge, been undertaken as a deliberate policy, probably due to liability concerns.

Now we see a series of reports and presentations (all pdf) by the Oklahoma Geological Survey showing a relationship between small earthquakes and fracking activity (the most important activity appears to be disposing of waste water in deep wells). Naturally, some people are concerned about liability.

Although many small earthquakes can be tied to oil and gas activity, no one has ever tied a large earthquake to such activity. And it is likely that no one ever will. Although the O&G activity is increasing the likelihood of small earthquakes, it is difficult to say what the impact on the likelihood of a large earthquake will be. The earth, even smaller parts of it, is a complex system, and part of what makes them interesting is that their response to stimulus is at least partially a function of the entire past history of the system. Our knowledge of earth history (especially around Oklahoma) is incomplete.

Suppose that in the absence of fracking, the recurrence interval for a magnitude 7.5 earthquake in a certain part of Oklahoma is on the order of 10,000 years (I have no idea if this is reasonable). Increasing the likelihood of small earthquakes may make a large earthquake more likely. If the last major earthquake in the area occurred in the 16th century, then probably there wouldn't have been enough time for the stresses in the system to build for a large earthquake to be triggered by fracking. But if the last big earthquake was ca. 10,000 BC, then there might be a problem.

There are costs and profits to be made from all kinds of human endeavours. Drilling for oil is one of them. I don't think we can allow the risks of induced earthquakes dissuade us from searching for oil, as it is a key determinant for economic progress. My concern is--are the people making the profits from oil exploitation going to be the ones paying the inevitable costs? 

Sunday, May 17, 2015

Zhuyu Peak

Apart from its natural beauty, Yuntaishan is also famous as one of the key places in the development of Taoisim. The highest point in Yuntaishan, and the site of an ancient temple, is Zhuyu Peak. A rapid bus ride up a winding road and through numerous tunnels brings you to a major platform about 200 m below the peak--you get to climb the rest of the way.



Part way up is the Cave of Medicine. Unfortunately, there is not much English documentation on the significance of the cave, but there is one document suggesting that Sun Simiao, the king of medicine during the Sui and Tang dynasties, made medicine here.



The cave has become a shrine, where people not only pray, but leave offerings (typically money) wedged into crevices in the cave walls.



Apart from the famous views, there is a temple complex. But it really isn't any different from any other temple complex in China.



The red tags represent prayers. Apart from the pagodas at the entrance, they are also left hanging from the railings all over the grounds.

Climbing back down from the peak, there is a trail that heads off about 2 km to the east, towards Phoenix Ridge. At the end of the path is a nice pavilion (seen below), as well as (you guessed it) another temple.




There was a lot of haze. At times, there was even fog. Later it began to rain, which complicated my descent somewhat.


The pavilion has a number of examples of paintings and calligraphy, but the lighting and reflections make most of them impossible to photograph.




Some views from the top of the pavilion.

From the pavilion, there is a 3 km walk down the side of the escarpment to Wanshan temple, which is about 800 m below the peak of the escarpment. Most of this drop occurs in the first km of the walk, which is almost entirely composed of stone stairs, occasionally without handrails.





It was raining, and I was concentrating very hard on not falling as the stairs were very narrow. I never saw anyone else the whole way down (it would be difficult to imagine anyone making this climb, except possibly as proof of devotion). It occurred to me if I took a tumble I might be in some difficulty as there was no cellphone reception at most points along the trail.

But there were advantages to the solitude. At times I would hear a sudden rustling of something big moving through the under brush. The first time it was on the ledge above me, and I jumped against the cliff and waited for the crash. Nothing. A little while later, I heard a sudden explosion of movement about 15 m to my right and a little below me, and just caught a glimpse of a wild macaque fleeing into the bush. It was the hands and feet that mostly stick in my memory. Probably it first froze as I was approaching until I got too close.


Thursday, May 14, 2015

Gold demand down (or is it?)

The World Gold Council has published its report on the global demand for gold. Get yours here.

The headline number: gold demand fell by 1% in Q1 '15 to 1079.3 tonnes (y.o.y).

In the section on gold demand statistics, we see that the dollar value of gold purchased in the Q1 '15 was about 7% lower than the value of gold purchased in Q1 2014 (p. 18, tables 2 and 3).

But remember--the US dollar is a whole lot higher over that time period. How much higher? Well averaging the weekly closing price of the US dollar index for every week in the Q1 2015 gives us an average value of 95.104--the same calculation for Q1 2014 gives us 80.359. That is an 18.3% gain.

The gold price itself fell about 7% over that time (in US dollars). But non-Americans purchasing gold in Q1 of 2015 are paying over 10% more that in Q1 2014. In this context, the 1% drop in physical takes on a different meaning. No wonder foreigners aren't buying so much!

Chinese jewellery demand is down fairly significantly. The report suggests that demand for securities trading may have eaten into gold demand. I can only report that the Chinese I speak to are convinced that since gold is going down it is a bad investment.



Thursday, May 7, 2015

The big, dry waterfall

Continuing through the park at Yuntaishan, you reach the Quanpu and Tanpu valleys (Quanpuxia and Tanpuxia in the local tongue).



It is a narrow valley cut down through predominantly limestone (with some intervals of sandstone), which is part of a platform that has been raised significantly by neotectonic activity over the past 25 million years.


The fractured zones of the rock are vulnerable to rapid erosion, hence the near vertical down-cutting by the rivers in this area.


After a long hike through the gorge, which is decorated by numerous small waterfalls and springs, you reach the highest waterfall in China--a 314 m drop.


Unfortunately it was dry. Now I want a refund.

The Tanpu valley is similar, but with working waterfalls (albeit smaller).




Unlike many rivers in China, this one at least had living things in it.


The last time I got to play with tadpoles was probably about 40 years ago.