Second, the NEIC collects and provides to scientists and to the public an extensive seismic database that S Geological Survey in A new geologic map of surficial deposits in the nine-county San Francisco Bay region that can be used to evaluate earthquake hazards has been released in digital form by the U.
Geological Survey in Menlo Park. A K2 seismograph. The K2 is an accelerometer and data-logger combined into a single, portable package. The unit is the size of a large shoe box.
It is usually installed in a corner of the garage or a convenient area on a patio or side walk along the house. A photo of a unit installed in a garage is shown. Shaking is. Bryant Platt digs a hole to install seismometers at a home in southern Kansas. Seismometers are in the foreground. Skip to main content. Search Search. Natural Hazards. There are many different ways to measure different aspects of an earthquake: Magnitude is the most common measure of an earthquake's size.
It is a measure of the size of the earthquake source and is the same number no matter where you are or what the shaking feels like. The Richter scale is an outdated method for measuring magnitude that is no longer used by the USGS for large, teleseismic earthquakes. The Richter scale measures the largest wiggle amplitude on the recording, but other magnitude scales measure different parts of the earthquake. The USGS currently reports earthquake magnitudes using the Moment Magnitude scale , though many other magnitudes are calculated for research and comparison purposes.
Intensity is a measure of the shaking and damage caused by the earthquake; this value changes from location to location.
Apply Filter. What is a Geoid? Why do we use it and where does its shape come from? Contrast of the Geoid model with an Ellipsoid and cross-section of the Earth's surface. Public domain. Seismometers, seismographs, seismograms - what's the difference?
How do they work? A second way earthquakes are measured is by their intensity. Earthquake Intensity measurement is an on-the-ground description.
The measurement explains the severity of earthquake shaking and its effects on people and their environment. There can be multiple intensity measurements as opposed to one magnitude measurement. Based on Giuseppe Mercalli's Mercalli intensity scale of , the modified scale is composed of increasing levels of intensity that range from observable quake impacts from light shaking to catastrophic destruction. Intensity is reported by Roman numerals.
An earthquake intensity scale consists of a series of key responses that includes people awakening, movement of furniture, damage to chimneys and total destruction. The size of an earthquake and the energy released by an earthquake will affect how much you feel it. Major earthquakes strike without warning , at any time of year, day or night. Whether you are a homeowner, mobilehome owner, condo-unit owner or renter, buy peace of mind with affordable and flexible earthquake insurance now.
Every day, Californians face earthquake danger. Our state has nearly 16, known faults and more than active faults. Most of us live within 30 miles of an active fault risk. Visit the CEA risk map for each county to learn about faults in your area. This information will help you survive an earthquake. Make your home more resistant to earthquake damage by assessing its structure, contents and need for loss of use earthquake insurance. Avoid financial disaster with loss of use coverage if your house sufferers extensive damage—get coverage with a CEA earthquake policy.
Decrease your risk of damage and injury from an earthquake by identifying possible home hazards. CEA offers earthquake home insurance premium discounts for houses and mobilehomes that have been properly retrofitted.
Without earthquake insurance, you place yourself at risk of losing everything or sustaining damages to your personal property that you cannot afford to repair or replace. CEA earthquake insurance not only helps repair damages. Create your account Lost password? First name. Last name. Your cart is empty. What Exactly is an Earthquake? Why Do Earthquakes Happen? Earthquake Lesson What is an Earthquake? Magnitude Explained: Moment Magnitude vs.
How Big was that Quake? Earthquake Basics PDF Earthquakes are now measured in two separate ways based on the amount of energy released at the epicenter and the intensity of the earth shaking that occurs in specific locations. Earthquake intensity is most often measured using the modified Mercalli scale , which was invented by the Italian geologist Giuseppi Mercalli in and uses Roman numerals from I to XII.
In the United States, we use the modified Mercalli scale, which was adjusted to account for differences in buildings between Italy and southern California. An earthquake intensity of I is generally not felt, and an intensity of XII represents total destruction of buildings. Some kinds of geologic deposits, most notably water saturated muds, amplify seismic waves and may produce intensities much greater than those for nearby areas underlain by bedrock. Thus, after an earthquake seismologists can interview people and make maps showing the intensity of an earthquake in different areas to better understand the influence of rock or soil type on seismic waves.
Large earthquakes are not measured very well by the Richter scale, especially if the seimometers used are very far away from an earthquake epicenter. The moment magnitude scale is now most commonly used for medium to large earthquakes. Details of how these scales compare are discussed by Rick Aster on page 8 and 9 of the Spring, issue of Lite Geology.
How do scientists measure earthquakes? With a really big ruler? No, not quite. There are two ways in which scientists quantify the size of earthquakes: magnitude and intensity.
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