How is richter magnitude measured

Another factor that contributes to the exact location of earthquakes is the way that energy tends to travels along a fault line, which can cause the overall size of an earthquake to be very large if the stress triggers tectonic plate movement along a long expanse of a fault line. The Richter scale was developed in the s and is most effective for large-scale earthquakes that are of moderate intensity. The Richter scale measures the maximum amplitude of seismic waves as they reach seismographs.

This scale is expressed with a logarithmic scale. Thus, an earthquake measuring 7. Very large earthquakes that measure more than 7.

For this reason, scientists now utilize more precise and advanced measurement methods. 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.

The moment magnitude scale measures the overall magnitude or size of the earthquake, and the modified Mercalli scale measures earthquake intensity. For the moment magnitude scale, scientists use a formula to convert the energy released, as measured by a seismometer.

Intensity measured by the modified Mercalli scale is assigned numbers between I and XII based on the amount of damage and reports received from eye witnesses.

At level I, vibrations are extremely minor, possibly felt by only a few people. Level II involves vibrations on the upper floors of buildings with suspended objects swinging slightly. At level V, everyone feels vibrations. The Richter scale is logarithmic , meaning that whole-number jumps indicate a tenfold increase. In this case, the increase is in wave amplitude. That is, the wave amplitude in a level 6 earthquake is 10 times greater than in a level 5 earthquake, and the amplitude increases times between a level 7 earthquake and a level 9 earthquake.

The amount of energy released increases As we previously noted, most earthquakes are extremely small. A majority of quakes register less than 3 on the Richter scale; these tremors, called microquakes , aren't even felt by humans. Only a tiny portion -- 15 or so of the 1. The biggest quake in recorded history was the 9. Generally, you won't see much damage from earthquakes that register below 4 on the Richter scale.

Richter ratings only give you a rough idea of the actual impact of an earthquake, though. 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.

The extent of damage is rated on the Mercalli scale. Mercalli ratings, which are given as Roman numerals , are based on largely subjective interpretations. 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.

Science Explorer. Multimedia Gallery. Park Passes. Technical Announcements. Employees in the News. Emergency Management. Survey Manual. Earthquake size, as measured by the Richter Scale is a well known, but not well understood, concept.

The idea of a logarithmic earthquake magnitude scale was first developed by Charles Richter in the 's for measuring the size of earthquakes occurring in southern California using relatively high-frequency data from nearby seismograph stations. This magnitude scale was referred to as ML , with the L standing for local.

This is what was to eventually become known as the Richter magnitude. As more seismograph stations were installed around the world, it became apparent that the method developed by Richter was strictly valid only for certain frequency and distance ranges. In order to take advantage of the growing number of globally distributed seismograph stations, new magnitude scales that are an extension of Richter's original idea were developed. These include body wave magnitude Mb and surface wave magnitude Ms.

Each is valid for a particular frequency range and type of seismic signal. In its range of validity, each is equivalent to the Richter magnitude. Because of the limitations of all three magnitude scales ML, Mb, and Ms , a new, more uniformly applicable extension of the magnitude scale, known as moment magnitude, or Mw , was developed.

In particular, for very large earthquakes, moment magnitude gives the most reliable estimate of earthquake size. Moment is a physical quantity proportional to the slip on the fault multiplied by the area of the fault surface that slips; it is related to the total energy released in the earthquake.

The moment can be estimated from seismograms and also from geodetic measurements. The moment is then converted into a number similar to other earthquake magnitudes by a standard formula.

The result is called the moment magnitude. The moment magnitude provides an estimate of earthquake size that is valid over the complete range of magnitudes, a characteristic that was lacking in other magnitude scales. The primary goal of U. Geological Survey USGS Natural Hazards Response is to ensure that the disaster response community has access to timely, accurate, and relevant geospatial products, imagery, and services during and after an emergency event.

Earthquakes are one of the most costly natural hazards faced by the Nation, posing a significant risk to 75 million Americans in 39 States. The risks that earthquakes pose to society, including death, injury, and economic loss, can be greatly reduced by 1 better planning, construction, and mitigation practices before earthquakes happen, and The U.

Cumulative number of earthquakes with a magnitude of 3. The rate of earthquakes began to increase starting around and accelerated in Red indicates the highest hazard, and gray indicates the lowest hazard. This map shows earthquakes above magnitude 4. There are earthquakes recorded. An earthquake of magnitude 4.