Last 48 hours in Kathmandu – a Mathematician's analysis of the earthquakes | Hacker News Reader

Last 48 hours in Kathmandu – a Mathematician's analysis of the earthquakes

younghamlet.blogspot.com

28 pointsanaxag0ras5 comments

USGS Aftershock Forecast for the Magnitude 7.8 Nepal earthquake of April 25, 2015

(as of April 26, 2015) In the coming week, USGS expects 3-14 M≥5 aftershocks of the magnitude 7.8 Nepal earthquake. Additionally, USGS estimates that there is a 54% chance of a M≥6 aftershock, and a 7% chance of a M≥7 aftershock during this one-week period. After this, in the following month and then the following year, USGS expects several M≥5 aftershocks, with a significant chance of M≥6 aftershock (greater than 50%). The potential for an aftershock larger than the mainshock remains, but is small (1-2% in each time period).

Felt earthquakes (i.e., those with M≥ 3 or 4) will be common over the next weeks to months. Based on general earthquake statistics, the expected number of M≥ 3 or 4 aftershocks can be estimated by multiplying the expected number of M>=5 aftershocks by 100 or 10, respectively. The expected location of the aftershocks will be in the zone of current activity and at its edges. Currently aftershocks are occurring in a zone extending approximately 200 km away from the mainshock epicenter.

This information is preliminary and subject to change.

from http://earthquake.usgs.gov/earthquakes/eventpage/us20002926#...

This is not a great analysis, and is kind of confusing.

  Things will improve, the law of math promises it.

Ah well, if a mathematician says the law of math promises it!

See Omori's law (and Båth's Law and the Gutenberg–Richter law), and the roughly 5% chance that this quake was a foreshock for an even bigger quake ("the 2002 Sumatra earthquake is regarded as a foreshock of the 2004 Indian Ocean earthquake with a delay of more than two years between the two events")

Agreed. Earthquakes are extremly unpredictable, the best we have is the USGS models and even then they provide very little information.

In Christchurch, New Zealand the M6.3 aftershock in February 2011 was far more destructive than the initial M7.2 event that occured 5 months earlier. This was because the epicenter of the February aftershock was significantly closer to the city and populated areas.

Looking at the Nepal aftershock sequence map [1] it is a concern that many of the aftershocks are located closer to the populated areas. I really hope that Nepal has had the worst of it but it would be a mistake to rule out the possibility of another major event.

[1] http://www.latimes.com/visuals/graphics/la-fg-g-nepal-map-qu...

But that contradicts the statements of a trained mathematician!

</sarcasm>

I'm not sure that "NASA / BBC / America" are trained seismologists, but if they're simply reporting the predictions of someone who really understands the conditions of the subduction zone in the Katmandu area, I'd tend to believe what they're saying.

The magnitude isn't everything, Christchurch NZ being a case in point. It's later, shallow earthquake caused much more destruction and killed many, while the bad initial quake killed no one directly. I'm no expert, but the magnitude of the quake is relative to the depth in a way that masks the actual destructive power.

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