What's new in exploration

	Vol. 227 No. 1
PERRY A. FISCHER, EDITOR

Predicting earthquakes. Predicting earthquakes is a sort of Holy Grail for geophysicists and seismologists. A small Israeli company named Terramoto has recently proposed a three-stage method of prediction, as well as a way to mitigate an earthquake’s strength.

The creator of the idea, Meny Nachman, focused on the root causes of earthquakes. According to the plate tectonics theory, plate intersections are areas where movement is irregular, creating regional fault lines. The variability of this movement is believed to be due to irregularities deep in the Earth’s crust.

These irregularities are attributed to obstacles, such as huge blocks, perhaps thousands of feet in diameter, and up to 12 mi deep. The hypothesis is that these blocks can locally stop movement along a fault line. This would cause the accumulation of strain, which would be suddenly released when the blocks finally fractures – hence, an earthquake occurs. Small earthquakes happen near fault lines frequently, although we usually do not feel them. The system developed by Terramoto’s Nachman regards them as precursors of an impending big earthquake. That part, at least, is not a new idea.

The three stages are mapping, predicting and, if possible, preventing major earthquakes from occurring along known fault lines. The mapping part is the easiest, using standard geophones placed along the fault line, essentially the same as has been done at the Parkfield site in California and other known earthquake-prone areas. If one of the stations shows anonymously low activity, while adjacent stations show high activity, the blocking hypothesis would assume that strain is building and not being released at the low-activity geophone.

Once a potential strain point is found, a deep seismic survey is acquired using oilfield equipment, the purpose of which is to locate the blocking obstacle. A borehole is then drilled to extract a rock core and evaluate its strength. This, combined with the seismic survey, determines limits on the size and shape of the obstacle. This data is then used to create “advanced mathematical models” that can predict how much pressure the rock could endure before collapsing from the sheer force of the tectonic plate. The amount of pressure buildup can be a good indication of the possible force the earthquake could unleash when the rock eventually shears. Timing would be achieved by using two laser interferometers, each placed on a different tectonic plate, to measure movement accurately and thus determine the rate of energy accumulation inside the rock.

Here is the weird, or at least daring, part. Once a high-magnitude earthquake has been predicted, the company would drill a well up to 6 mi deep to place explosives inside the rock. A series of “controlled” blasts would weaken the rock, gradually relieving the built-up energy accumulated over the years.

Much of the monitoring and drilling is already being done in projects such as EarthScope. That project recently installed a long-term geophone array in a borehole that penetrated the San Andreas Fault.

IsraCast, a news agency from which this report was taken, spoke with Dr. Shmulik Marco from the Department of Geophysics and Planetary Sciences at Tel Aviv University, to get his view on the method. His interesting comment was that although there are some technological obstacles in the way – not the least of which is the drilling depth – the main reason such systems have not been implemented in the past is more political then technological. He was referring to funding.

Most of you reading this are probably aware that there are various schemes along these lines that have been proposed for many years. Assuming that one could get the funding, determine the “stuck point,” and drill to the required depth, the last point about downhole detonation is a bit scary. Whatever the reason for the “stuck” condition along the fault, it could require some truly massive amounts of explosive energy to free it.

I’m not sure that we know enough to go down this path. Reminds me a bit of the soldiers who witnessed the first atomic bombs, wearing only sunglasses. With the gift of hindsight, we were idiots to do that. Truth be told, we are still idiots. We always will be idiots. We have but little choice to use the information we have, to the best of our abilities. Detonating however many thousands of pounds of explosives it takes to free a stuck fault could have some unforeseen circumstances. For now, this unique for-profit business should stick to proving the prediction part. That, alone, will be difficult, and useful, enough.

GOM discoveries summary. The MMS put out a summary table of the deepwater discoveries made in through December 1, 2005. Using the 1,000-ft mark as a deepwater definition, there have been nine oil and gas discoveries.

Chris Oynes, MMS Regional Director for the Gulf of Mexico, said, “Discoveries like BP’s Stones represent a continuing favorable development in the new Paleogene play in the Walker Ridge area.” The report noted that as of December 2, there were nine rigs drilling in ultradeep water – 5,000 ft deep or greater. There were seven at the same time last year.

MMS also noted that Chevron/ Unocal had reached a new drilling record in the GOM – 34,189-ft MD drilling depth at its Knotty Head prospect in Green Canyon Block 512. This broke the old record set by Shell of 32,727-ft MD.