Sorry about the light posting last week, but I had a bit of an adventure.  Let me tell you about it.

One of my favorite articles of all time was published in 1993 in the Bulletin of Atomic Scientists.  Called “Sleuthing From Home,” Vipin Gupta and Phillip McNab detailed their  effort at VERTIC to use commercial satellite imagery and seismic networks to detect, characterize and announce a Chinese nuclear test before the Chinese government did. Today, it would be quite a bit of work.  Twenty-years ago?  It was career-altering.

Over the past week I had my own “sleuthing from home” experience.  NNSA beat me and two colleagues to the punch, but just barely.

On Tuesday, Eric Berenson, a long-time blog reader, noted an unusual seismic event at the Nevada National Security Site — better known as the Nevada Test Site:

For years I have been looking at the USGS website for earthquakes that occur exactly on the hour or half hour, or that have a depth of 0km. Used to see them back 6 or 7 years ago but then they stopped. I check almost everyday and this morning I spotted one. I saved all the info and the waveforms. Here is what I saw:

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Magnitude 2.1
Date-Time Tuesday, July 24, 2012 at 11:00:00 AM at epicenter Location
37.224°N, 116.062°W
Depth 0 km (~0 mile) set by location program Region NEVADA

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This looks like Rainer Mesa. I didnt check on a map yet but it sure looks like it. So I went back to the USGS site a couple of hours later and it was REMOVED. Since when does the USGS remove earthquake data from public circulation ? Do they really do that?

This certainly looked like a man-made explosion.  The location (at the Nevada Test Site), the depth (shallow) and the time (11:00 am on the dot) all scream “it go boom.”  We had a probable 2.5 metric ton (Mb 2.1=4.05 + 0.75 logY) explosion at the Nevada Test Site (37.224N, 116.062W +/- 0.9 km).

The fact that USGS subsequently deleted the event entry (here is the dead link) struck me as very interesting.

I sent off two emails — one to the University of Nevada-Reno, which operates the regional seismic network in Nevada, and another to the United States Geological Survey.

The first email I received, from UNR, explained that the event was removed from the main website because it had been determined to be a “blast” and not an earthquake. An entry for the event remained online.  The researchers were straightforward and transparent in their response. You know, like scholars.

The second email I received, from USGS, was more like what one expects from bureaucrats.  Non-responsive. Not helpful. Possibly dissembling, although that implies a level of attention to my email that seems unrealistic. An entry for the event has now reappeared elsewhere, but I am still not convinced the removal was simply because the event was small.

With the confirmation that the event was a blast, I emailed Nick Roth, who knows more about what NNSA is doing than just about anyone at NNSA.  Nick and I were able to make further suppositions about the nature of the event at NTS.  We could exclude a subcritical test gone very wrong at U1a, as well as a conventional explosion at the BEEF (Big Experimental Explosives Facility).  Those two locations were just too far away from the hypothesized epicenter.

That left one option — but NNSA beat us to announcing it.  NNSA announced that it conducted seismic Source Physics Experiment-3:

The National Nuclear Security Administration (NNSA) today announced that it has successfully conducted the third seismic Source Physics Experiment (SPE-3) at the Nevada National Security Site (NNSS). The seismic experiment was the third in a series of seven underground, fully-coupled, high-explosive field tests.

SPE-3 included detonating a chemical explosive equivalent to 2,200 pounds of TNT in a contained, confined environment 150 feet below ground.

I think we would have figured it out eventually — all three experiments (including SPE -1 and SPE-2) were conducted within a few hundred meters of the hypothesized epicenter for our event.  Here is a map showing the location of SPE-series:

One of the other slides contains the latitude/longitude.  That’s the same spot as the hypothesized epicenter of our event.  Indeed, 2011 satellite images show what appear to be preparations for previous SPEs. (You could do a nice overlay if you had the time.)

In general, I want to compliment NNSA on making available all this information.  One detail, however, that NNSA seems careful to obscure is the date for SPE-1, SPE-2 and SPE-3.  Keeping the date a secret might explain why these events don’t appear in certain catalogues.  I am not okay with that.

Three observations about our little adventure.

First, regional seismic networks offer exquisite monitoring capabilities.  The US network detected a 1 ton event, correctly identified it as an explosion and located it within a few hundred meters.  As a demonstration of the power of regional seismic monitoring, this is jaw-dropping.  The fact that much of this was possible on an open-source basis was pretty cool, too.

Second, I am not convinced of the integrity of the data provided by US Geological Survey.  Events with an Mb less than 2.5, should appear in the ANSS catalogue, but this one does not — nor can I find plausible entries for SPE 1 and 2.  (I searched for similar magnitude events in the same area. I made sure to check “all events” as well as “events with no reported magnitude.”  Perhaps I am still doing something wrong, but as best I can tell USGS deleted these events.)

Consider a future researcher who claims (incorrectly) that the regional monitoring network “missed” the SPEs — series of large explosions conducted for the very purpose of CTBT verification at NTS.  How would anyone know this was incorrect, unless some blogger-scum noticed USGS deleting the event in real time and then observed it had not been submitted it to ANSS?

Eric observed that he stopped seeing anthropogenic events (on the hour, zero depth) about six or seven years ago.  That may point to a policy change that has persisted into the Obama Administration.  I wonder if the Director of USGS, Marcia McNutt, is aware of such a practice and whether she would defend it.

Third, even if the removal of “blasts” is a transparent decision, I still think it sets an  unhelpful precedent from a national security perspective. I understand that most people are interested in only earthquakes, but some other people are interested in treaty verification.  These are both legitimate interests served by collecting seismic data.

Iran, for example, has an exquisite regional earthquake monitoring network that could provide significant monitoring capability against any Iranian nuclear test.  Imagine the reaction if Tehran openly admitted to systematically removing man-made explosions from that data set?

A precedent of removing explosions from seismic catalogues would prevent one of the best confidence building measures we might pursue with with regard to Iran’s nuclear program and the Comprehensive Nuclear Test Ban Treaty — exchanging real-time regional seismic data. The three best regional monitoring networks in the world are based in Iran, Japan, and the Western United States.   One of my goals is encourage Iran to share regional seismic data on a real-time basis with one of these comparable networks — Japan is probably easiest.  Data exchanges would help both countries collaborate on disaster response by learning how the other detects, characterizes, warns and responds to earthquakes rapidly (a Japanese specialty I  experienced first hand).  The fact that this collaboration would also have a significant nonproliferation benefit is a nice side-benefit.

Of course, there is no nonproliferation benefit if states routinely engage in monkeying with the data.