Earth Science: EarthQuakes – Prediction and Safety
Earthquake prediction is still an inexact science; however, monitoring systems are constantly improving. With adequate preparation the worst consequences can be avoided. Without it, the scale of disaster can be enormous.
Many phenomena can precede an earthquake: Rock deformations cause changes in the active plate boundaries of Earth’s crust. When water seeps from rock pores, groundwater level can change. Earth columns that open up also influence soil’s electrical conductivity. Rock fissures release radioactive gases onto Earth’s surface. Eventually, smaller tremors cause a large quake.
All of these events can be measured by the equipment at seismological stations. Even unusual animal behavior can predict an imminent earthquake. However, such signals are not sure indicators. Earthquakes and tremors can occur without any indication at all. Prospective early warning systems are thus being investigated.
Recently, activity levels of positively charged oxygen (O2) ions have been used as predictors of seismic activity. O2-ions originate in the interior of the Earth when O2 molecules are destroyed and rise to the surface, combining with oxygen in rocks to release energy as heat. A satellite-supported system may be able to detect such emissions, providing early warning of seismic events in time to sound the alarm.
Tsunamis
Most tsunamis are triggered by seaquakes that cause vertical shifts of the ocean floor, setting the water above in motion and forming circular waves on the open sea. Unlike storm waves, in which only the uppermost layer of water is raised, all of the water in a tsunami wave is raised, making it extremely powerful. When a tsunami approaches a coastline, its
waves increase in height because of the decrease in water depth and in response to the wave’s decreasing speed.
The rising waves that make up tsunamis cause widespread, catastrophic damage. In fact, even the wave troughs that accompany tsunamis can cause destruction, sucking out to sea anything with which they come into contact—often up to a mile from shore.
MODERN SKYSCRAPERS
Modern skyscrapers are designed to withstand earthquakes up to 8.5 on the Richter scale. Some buildings are supported by large steel and concrete columns that intertwine to form a movable “corset” that swings with the tremors instead of resisting them.
Other buildings are constructed on bearings that can neutralize the effects of Earth’s vibrations or use vibration compensators such as enormous hanging steel balls. The Torre Mayor in Mexico City, built in 2003, uses seismic dampers.