![]() One of the downfalls of this scale is it has an upper limit on highest measurable magnitude. The amplitude of the waves increases by powers of 1- in relation to the Richter magnitude numbers. The numbers on the scale range from 0-10. Adjustments are made to compensate for the differences in distance between seismographs and the epicenter of the earthquake. A seismograph functions by a weight that is freely suspended from a support that is attached to bedrock and each wave is recorded as the weight moves. Information of seismic activity is gathered using a seismograph. It is also known as the local magnitude scale. It was designed to measure medium-sized quakes (3.0-7.0) in Southern California. The Richter Scale was developed in 1035 by American seismologist Charles F. For many years the magnitude from the seismic waves from these quakes have been measured with the use of the Richter Scale. Some so slight they can’t be felt, while others, which occur much less frequently, can cause catastrophic damage. When there is a shift in the tectonic plates an earthquake occurs.Įach year worldwide thousands of earthquakes occur. Cracks in these plates are called fault lines. These plates are actually huge slabs of rock 50-650 feet (15-200 km) thick. Once they have a good idea of the range of damage, they use the Mercalli criteria to decide on an appropriate rating.The earth’s continents and seas are carried on underground oceans of extremely hot and semi-solid materials by tectonic plates. Mercalli ratings, on the other hand, can't be determined until investigators have had time to talk to many eyewitnesses to find out what occurred during the earthquake. Richter scale ratings are determined soon after an earthquake, once scientists can compare the data from different seismograph stations. The highest rating, a XII, is applied to earthquakes in which structures are destroyed, the ground is cracked and other natural disasters, such as landslides or tsunamis, are initiated. A low intensity earthquake, one in which only some people feel the vibration and there is no significant property damage, is rated as a II. Mercalli ratings, which are given as Roman numerals, are based on largely subjective interpretations. The extent of damage is rated on the Mercalli scale. As we've seen, an earthquake's destructive power varies depending on the composition of the ground in an area and the design and placement of man-made structures. Richter ratings only give you a rough idea of the actual impact of an earthquake, though. Generally, you won't see much damage from earthquakes that register below 4 on the Richter scale. It killed nearly 1,900 people and caused about $4 billion in damage in 2010 dollars. The biggest quake in recorded history was the 9.5 quake that struck Chile in 1960. Only a tiny portion - 15 or so of the 1.4 million quakes that register above 2.0 - register at 7 or above, which the threshold for a quake being considered major. A majority of quakes register less than 3 on the Richter scale these tremors, called microquakes, aren't even felt by humans. The amount of energy released increases 31.7 times between whole number values.Īs we previously noted, most earthquakes are extremely small. That is, the wave amplitude in a level 6 earthquake is 10 times greater than in a level 5 earthquake, and the amplitude increases 100 times between a level 7 earthquake and a level 9 earthquake. ![]() In this case, the increase is in wave amplitude. The Richter scale is logarithmic, meaning that whole-number jumps indicate a tenfold increase.
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