Archive for January, 2012

Prime Minister Noda Removes Eye Patch

The cover-up has come to an end! Prime Minister Noda has removed his eye patch:

He’d been wearing the patch for the last two weeks:

Complete with patch – more surgical than piratical — the premier later explained to reporters that the self-inflicted blow came in the dark as he rushed to try to pick up an unexpected call.

“The phone suddenly rang in the middle of the night,” the prime minister explained, “so I got up and rushed to get it, and then bumped into a pillar.”

Now he’s just wearing makeup to hide the bruises.

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The Tsunami and the Cherry Blossom (Academy Award Nominee – Best Documentary Short)

The trailer for “The Tsunami and the Cherry Blossom,” a short documentary about the aftermath of the March 11th disaster:

Survivors in the areas hardest hit by Japan’s recent tsunami find the courage to revive and rebuild as cherry blossom season begins.

A stunning visual poem about the ephemeral nature of life and the healing power of Japan’s most beloved flower.

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Earthquakes Cannot be Predicted / Official Japanese Quake Forecasting System is Flawed

If you’ve been watching the news the last few days, chances are you’ve heard about that researchers are now saying that Tokyo is facing a 70% chance of a 7.0 magnitude earthquake in the next four years:

The preliminary calculations conducted by a team from the university’s Earthquake Research Institute were based on intensified seismic activity in the area after the Great East Japan Earthquake on March 11.

The findings are more dire than a similar estimate by the central government’s Headquarters for Earthquake Research Promotion, which states there is a 70 percent chance a quake of the same scale will hit the southern Kanto region, including the metropolitan area, within 30 years.

Sounds pretty scary. Should we believe the forecast? Not necessarily.

In April of 2011, Nature published “Shake-up time for Japanese seismology” by Professor Robert J. Geller of Tokyo University (Japanese version available here). Geller argues that earthquakes cannot be reliably predicted.

When one compares the Japanese government’s national seismic hazard map to the actual areas where large earthquakes have occurred in the last 30 years, one notices the problem:

“Although such maps may seem authoritative, a model is just a model until the methods used to produce it have been verified. The regions assessed as most dangerous are the zones of three hypothetical ‘scenario earthquakes’ (Tokai, Tonankai and Nankai; see map). However, since 1979, earthquakes that caused 10 or more fatalities in Japan actually occurred in places assigned a relatively low probability. This discrepancy — the latest in a string of negative results for the characteristic earthquake model and its cousin, the seismic-gap model — strongly suggests that the hazard map and the methods used to produce it are flawed and should be discarded.”

Very general predictions are possible:

“If global seismicity and the historical record in Tohoku had been used as the basis for estimating seismic hazards, the 11 March Tohoku earthquake could easily have been ‘foreseen’ in a general way, although not of course its particular time, epicentre or magnitude.”

But the Japanese government continues to rely on methods that attempt – and apparently fail – to predict earthquakes of specific magnitudes taking place in specific regions.

“All of Japan is at risk from earthquakes, and the present state of seismological science does not allow us to reliably differentiate the risk level in particular geographic areas. We should instead tell the public and the government to ‘prepare for the unexpected’ and do our best to communicate both what we know and what we do not. “

Much of Geller’s article focuses on the Japanese government’s official Tokai earthquake prediction. However, the general message is clear: there is no reliable method for forecasting earthquakes.

The latest forecast for Tokyo does not appear to represent a sudden new breakthrough in the field of earthquake predictions. What’s new about it is that heavy emphasis is placed on the increase in seismic activity that occurred in the 6 months following the March 11th disaster. [For a detailed analysis of the forecast - see this post. ]

Some of the articles about the new Tokyo prediction have presented it alongside the highly questionable Tokai earthquake prediction. Both predictions are based on methods that have not been verified as accurate.

Don’t trust the hype. Big earthquakes do happen in Japan, but experts do not know where and when the next big one will occur. If you live in Japan, be prepared for earthquakes, even if you’re outside of what have been deemed high risk areas.

[gigantic hat tip to Steve]

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How a 70% Chance of a M7 Earthquake in 4 Years was Calculated

Are you wondering how a group at the Tokyo University Earthquake Research Institute (ERI) calculated a 70% chance of a Magnitude 7 quake occurring in the Tokyo area within the next four years? If so, take a look at the above plot of historical Japanese earthquake data that compares the number of quakes per year to the total energy released by each quake.

First of all, ERI didn’t do this from scratch. They started with a potentially flawed government calculation and suggested a new value based on recent observations. This new value is 98% chance within 30 years, which translates to 70% in 4.

Now to the plot. let’s consider the filled symbols, which represent data spanning as much as the past 55 years, up to 2010. The frequency of earthquakes rapidly and predictably decreases with magnitude, meaning larger quakes happen much less often than smaller ones. The relationship between frequency and magnitude is shown by the dashed lines. One line doesn’t fit the entire dataset. Rather, the occurrence of quakes in excess of M4 decreases more rapidly with size (and therefore plot along a different line).

Next, let’s look at the open blue circles, which are about 6 months worth of data, from March 11 to August 1, 2011. As you can see, these data exhibit a similar slope but plot significantly higher than the pre-3/11 data. This indicates that higher-magnitude earthquakes have occurred more frequently since 3/11, a fact of which anyone living in eastern Japan is keenly aware. There appear to be too few occurrences of quakes larger than M4 to calculate a robust fit, (i.e., no corresponding dashed line) though it appears that the slope for the larger quakes is also similar to the pre-3/11 data.

Finally, we come to the new prediction. In the bottom right of the plot, the government’s official prediction of a M6.7 – 7.2 quake occurring in Tokyo is overlain as a yellow star and horizontal solid line. The folks at ERI simply recalculated this based on the  equation for the extrapolated fit between earthquake frequency and magnitude since 3/11.

There you have it. That’s how they did it. But is it correct?

I’d argue that this analysis, while interesting, contains several important flaws.

1. The new prediction is based on extrapolation from a perturbed state. That is, the frequency of earthquakes is currently elevated but likely to drop to normal over time.
2. It is based on very few observations.
3. It is based on extrapolation beyond the limits of the data.
4. It appears to be based on an inappropriate equation (the M4 and smaller frequency/magnitude relationship).
5. It does not account for uncertainty.

Most importantly, the correlation between frequency and magnitude breaks down for large quakes in the pre-Tohoku dataset, and if calculated, would be significantly lower for the M4 and greater quakes since 3/11. Could this increased uncertainty yield a result that is statistically indistinguishable from the government’s prediction? Maybe, but without the raw data, I can’t  say for sure.

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Contributor Bio: Steve has been splitting time between the US and Japan for the past 10 years or so and is now a researcher at a Japanese university.

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