Life is full of questions

The image above may take you way back to your days of grade school. It is the cross-section of the earth - handily delivered to us courtesy of our ever-helpful scientists. This image (or similar images) has been taught to us in grade school for generations - my dad even learned this in grade school. He was born in 1946.

One thing that I've often wondered about regarding this image: how did scientists (at least prior to the 1950s) know that this is really how the earth looked millions of miles below the surface? Was the equipment really that sophisticated then? Really? Seriously? Are you sure?

If we truly possess the capability of looking so deep in the earth with such precision, then how come it is that we still drill "dry holes" when drilling for oil just thousands of feet below the earth's surface?

Then, just yesterday evening, I saw an alarming newstory on the 6 o'clock news: there's been a brand new (within the past 18months - 2 years) discovery of a30-mile earthquake fault line in the Mississippi River just northwest of Memphis, Tenn. I've found several links to the story here and here. I'll quote liberally in case the links are changed/damaged in the future:

"MEMPHIS — Using new techniques to scan sediments thousands of feet beneath the Mississippi River bottom, University of Memphis researchers noticed a troubling crack that showed up like a bone fracture on an X-ray. It was an earthquake fault — crisscrossing the river in front of Memphis. Up to a mile deep and stretching at least 25 miles from Meeman-Shelby Forest State Park to the Ensley Bottoms area, the fault could have produced an earthquake of up to 7.0 in magnitude sometime in the last 1.8 million years, the researchers and officials announced Friday."

"MEMPHIS, TN (WMC-TV) - Officials expressed new concerns Friday about the devastating damage a newly discovered fault line could cause to the Mid-South. It's called the Meeman-Shelby Fault, and officials say it could be a devastating blow to Memphis if activated.
'If this fault goes, then there will be widespread damage,' Beatrice Magnani of the University of Memphis said Friday. University of Memphis researchers recently discovered the 30 mile long fault under the Mississippi River, along the Western border of the Shelby-County line near Shelby Forrest. Researchers say if the fault becomes active, it could trigger a 7.0 magnitude earthquake. That's why officials say now is the time to plan."

Wow.

This sounds serious.

What I don't understand is how, if we have such super sophisticated technology (that can tell reveal to us the precise layers of the earth's inner structure and that the sun's temperature is 11,000 F), are we only just now able to locate a mile-deep series of fissures in our own backyard?