Here's a link to NASA scientist Friedemann Freund's study on the eletromagnetic changes that occur in the earths crust prior to a quake occuring. He explains: "If the stress level is high, electronic charges appear that momentarily turn the insulating rock into a semiconductor," he said. Semiconductors are materials that have a level of electrical conductivity between that of a metal and an insulator, and they are used to make transistors.

"These charges are not easy to pin down. They move with impressive speed, as fast as 300 meters (1,000 ft.) per second," he said. By measuring the semiconductor properties of the rocks, Freund was able to show that the charges are positive. "Normally, these charges are dormant," he said. "But when rocks are squeezed, the charges wake up and flow out of the rock volume in which they were generated."

When charges flow, they constitute an electric current. When there is an electric current, there also is a magnetic field. If current varies with time, electromagnetic waves will be emitted. "The frequency of these electromagnetic waves will probably be very low, much lower than radio waves, but basically of the same nature," said Freund. "Scientists can pick them at the Earth's surface with suitable antennae or by measuring the magnetic-field pulses that go with them."

Low frequency magnetic-field pulses...Sounds like ULF to me. Somebody tell me why these detectors aren't located 40km apart for every square inch of California. They should be.

Billion

• Positve signals in earths crust