Locating EarthQuakes

An earthquake is located by computing its distance from each seismograph station that recorded the quake.
An arc of appropriate radius is drawn around each station; the quake lies where the arcs intersect.

The Best Soil

The most ideal soil conditions to be standing on, whether it be building or beast, is bedrock -- deep and unbroken rock formations and stiff soils.
Unlike soft soils, sand and gravel, water-saturated soils, there is far less vibration transferred through bedrock foundations and in turn to the structure above.

Jan 14, 2001 - New Zealand

The Institute of Geological and Nuclear Sciences, Victoria University of Wellington, reported a 3.4 earthquake at 6:53 am. It was 10 km east of Wellington.
Two other quakes were recorded the day before, one in Southern California and a significant Quake in Mexico.

Recording Quakes

The principal instrument used to record earthquakes is the seismograph, the name of which derives from Greek words meaning "earthquake" and "to write." The main function of a seismograph is to record vibrations in the ground. The most modern form of seismograph is basically a weight suspended by springs in such a way that its own inertia tends to keep it still when the ground moves under it.

Earthquake Waves

Earthquake Waves are vibrations in the earth that produce the shaking. They are in the form of waves of several kinds. The waves are transmitted by the displacement of particles, which in turn shove against and displace particles next to them, causing the advance of the disturbance.

New Zealand

This was a question from a viewer: Why does New Zealand have earthquakes?
A: Australia and the Pacific meet along the Alpine Fault, and the Eastern South Island is colliding and sliding southwards (and uplifting the Southern Alps in the process).
New Zealand straddles the boundary of two tectonic plates, the Pacific Plate and the Australia Plate, which move approximately 40 millimeters per year. This movement has been directly linked to volcanic and earthquake activity.
Trimble GPS receivers are used to measure the movement.

Tectonic Plates

This is a theory that unifies many the characteristics and features of Continental Drift. This theory holds that the Lithospere is divided into about 7 major plates with (to the best of our knowledge) 12 smaller ones roughly 60 miles thick, which rest on a soft layer called the asthenosphere. The 25 mile thick continents are embedded within some of these plates, the rest are along the ocean floor.
What moves them is still unknown.

Causes of Quakes - Past Beliefs

In early times, people believed that the earth was fixed in space and that the sun, moon, and stars rotated around the earth. They naturally concluded that the earth must be fixed on some sort of support and earthquakes were then quite reasonably attributed to movements in that support.
In Japan at one time, the support was believed to be a great spider, and later a giant catfish. In Mongolia and the Celebes it was believed to be a hog; in India, a gigantic Mole; in some parts of South America, a whale; and among some of the North American Indians, a giant tortoise.

Quake Zones

The Pacific Ocean, the area of the Mediterranean, and Asia release 95% of the world´s seismic energy.

Alfred Wegner

Alfred Wegner was a German meteorologist that proposed the theory (1912) that the earth was not fixed - it "moved" on plates. Come to find, in the 1960s, Alfred Wegner´s theory was proven correct. This theory is known as Continental Drift.

Epicenter

It is commonly thought that the Epicenter of a quake is the point of origin. However, that is actually called the FOCUS. The FOCUS is the source of an earthquake - it´s beneath the surface of the earth. The Epicenter is the point directly over the FOCUS on the surface of the Earth´s crust.

Volcanoes

Earthquakes do not cause volcanic activity. to that is Different earth processes are responsible for volcanoes. Earthquakes may occur in an area before, during, and after a volcanic eruption, but they are the result of the active forces connected with the eruption, not the cause of volcanic activity.

Causes of Quakes - Current Knowledge

The cause of earthquakes is ultimately related to a universal mobility of the earth´s surface. There is evidence of the existence of forces constantly at work molding the "skin" of the globe. However, the origins of such forces is still not entirely known.
Evidence is supplied by the data of structural and historical geology. Every mountain range in the world today consists in large part of sedimentary rocks that were at one time formations on the bottom of the ocean. Theories concerning the ultimate causes of the mobility of the earth´s crust have had their origin, for the most part, in attempts to explain the complex process of mountain making.

EarthQuake Sounds

As a rule, the beginning of the sound precedes the first shock to be felt, the largest sound accompanies the greatest shaking, and the end of the sound coincides with the end of the shaking. There are many exceptions to this rule but, it´s difficult to assemble reliable statistics to this phenomenon. The sounds are described in various ways but, they are usually consistent as low and booming.
Very near the source the sound sometimes includes sharp snaps that suggest the tearing apart of great blocks of rock. Farther away, the sounds are likened to heavy vehicles passing rapidly over hard roads, the dragging of heavy boxes over the floor, a loud but distant clap of thunder, an explosion, and the boom of a distant cannon.