EARTHQUAKES AND VOLCANOES
Earthquakes are the vibrations in the ground that result from movement along breaks in Earth's lithosphere. These breaks are called faults.
The greater the force applied to a fault, the greater the possibility of a large and destructive earthquake.
Records show that most earthquakes occur in the oceans and along the edges of the continents.
Earthquakes are the result of the accumulation and release of stress along the boundaries of the active plates. Some earthquakes occur more than 100 km below the Earth's surface.
The deepest earthquakes occur when plates collide along a convergent plate boundary.
Earthquakes that occur along convergent plate boundaries usually release huge amounts of energy. They can also be disastrous. Shallow earthquakes are common where plates separate along a divergent plate boundary, such as the oceanic ridge system.
Continental collisions result in the formation of large, deformed mountain ranges
When a force is applied to the rock, depending on the properties of the rock and the application of Boece, the rock may bend or break when a force such as pressure is applied to the rock along the plate, the rock may change shape. This is called rock deformation.
Faults: A fault is a rupture in the Earth's lithosphere where one shelf Nt moves toward, away from, or past another. The direction in which the rocks move on both sides of the fault depends on the forces applied to the fault. These faults are called sliding, normal, and reverse faults.
Types of faults: 1. Strike-slip:are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally. If the block opposite an observer looking across the fault moves to the right, the slip style is termed right lateral; if the block moves to the left, the motion is termed left lateral. 2. Normal: fault in which the block above the fault has moved downward relative to the block below. 3. Reverse:is the opposite of a normal fault—the hanging wall moves up relative to the footwall.
Earthquake Focus y Epicente: When rocks move along a fault line, they release energy that travels as vibrations on Earth called seismic waves. These originate where the rocks first move along the fault, at a place inside the Earth called the Farth. Earthquakes can occur anywhere between the surface of Farth and depths of more than 600 km.
The epicenter is the location of the Earth's surface directly above the focus of the earthquake.
Types Seismic Waves: The three types of seismic waves are primary waves, secondary waves, and surface waves.
Seismic Waves: During an earthquake, a rapid release of energy along a fault produces seismic waves. Seismic waves transfer energy through the ground and produce the movement felt during an earthquake. The released energy is strongest near the ep-center. As the seismic waves move away from the epicenter, they decrease in energy and interest.
Types: 1. Primary Waves: Primary waves, also called P-wuves, are purticulated in the ground to move in a push-pull motion similar to an ileal spring. P-waves are the fastest moving seismic waves. They are the first waves you feel after an earthquake.
2. Secondary Waves: Secondary waves, also called S-waves, are slower than P-Waves. They cause the particles to move up and down at right angles to the direction the wave is traveling. This motion can be demonstrated by waving a coil spring from side to side and up and down at the same time.
3. Surface Waves:Surface waves cause particles on the ground to move up and down in a continuous motion, similar to ocean waves. Surface waves travel only on the surface of the Earth closest to the epithelium.
Mapping Earth's interior: Scientists who study earthquakes are called seismologists. They use the properties of the seismic "we" to map the interior of the Earth. P-waves and S-waves change speed and direction depending on the material they are traveling through. Seismologists have discovered that S-waves cannot pass through the outer core. This discovery showed that the Earth's core is liquid unlike the solid inner core. In addition, seismologists have discovered that the inner and outer cores are composed primarily of iron and nickel.
The seismic waves tend to slow down as they travel through the hot pair.
Locating an Earthquake's Epicenter:An instrument called a sinusoidal seismometer measures and reconnects the ground and can be used to determine the wnes uvet dysrstum. The ground motion is called a seismogram, a graphic set of seismic waves.
Determining Earthquake Magnitude:Scientists can use three different scales to measure and decipher earthquakes: The Richter Seismological Scale, or Local Magnitude Scale (LM), is an arbitrary logarithmic scale that assigns a number to quantify the energy released in an earthquake, named after American seismologist Charles Richter.
The energy released depends on the size of the fault that breaks the movement that occurs along the fault and the resistance of the rocks that break during an earthquake. The units of this sa are exponential. For each unit increase in scale, t earthquake releases 31.5 times more energy.
Describing Earthquake Intensity: Another way to measure and describe an earthquake is to assess the damage resulting from the tremor. The tremor is directly related to the intensity of the earthquake. The Modified Mercalli Intensity value assigned to a specific site after an earthquake has a more meaningful measure of severity to the nonscientist than the magnitude because intensity refers to the effects actually experienced at that place.
Earthquake Risk:Most earthquakes occur near the boundaries of tectonic plates. The transform plate boundary in California and the convergent plate boundaries in Oregon, Washington, and Alaska have the highest earthquake risks in the United States. However, not all earthquakes occur near the plate boundary. Some of the largest earthquakes in the United States have occurred far from the plate. boundaries. Because earthquakes threaten people's lives, seismologists study the likelihood of an earthquake occurring in a given area. Probability is one of several factors that contribute to earthquake risk assessment. Seismologists also study past seismic activity, the geology around a fault, population density, and building design in an area to assess risk. Engineers use these risk assessments to design earthquake-proof structures that are able to withstand the shaking during an earthquake.