Measures of an earthquake magnitude and intensity pdf

Over the next 20 years richter and many other workers extended the scale to newer seismometers, different regions, and different kinds of seismic waves. Pdf significant earthquake intensity measures for seismic. Ground motion intensity measures for performancebased. There are two fundamentally different types of scales commonly used by seismologists to describe earthquakes. Earthquakes can be measured in terms of either the amount of energy they release magnitude or the degree of ground shaking they cause at a particular locality intensity. Additionally, diverse structural failures are exposed to manifest their seismic damage potential. This was later revised and renamed the local magnitude scale, denoted as ml or m l. More than 8000 houses collapsed and 40,000 were damaged. Tsunamis typically originate at undersea boundaries of tectonic plates near the edges of continents, he said. Several scales have been defined, but the most commonly used are. Earthquake magnitude, intensity, energy, and acceleration 107 be about 16 kin. In case of an earthquake move out of the building and came in. A critical issue in the pr obabilistic framework for performa nce based earthquake engineering is the choice of ground motion intensity m easures.

Earthquake magnitude is a fundamental parameter used to quantify and compare the size of large and small earthquakes. Earthquake a has a richter magnitude of 7 as compared with earthquake bs 6. Pdf earthquake magnitude measurements for puerto rico. Measuring earthquake magnitude and intensity geokansas. Youll notice that m l really measures the size of earthquake waves, not an earthquakes total energy, but it was a start. There are two ways to think about the duration of an earthquake. The focus on overall magnitude measures leads people to ignore the factor of distance in earthquake damage. The first is the length of time it takes for the fault to rupture and the second is the length of time shaking is felt at any given point e. The effects of earthquake significant duration d595 to the earthquake intensity measures and the inelastic response of sdof reinforced concrete structure. The moment magnitude scale measures the total energy released by an earthquake. The richter magnitude scale measures the amount of seismic energy released by an earthquake.

Prior to the development of the magnitude scale, the only measure of an earthquake s strength or size was a subjective assessment of the intensity of shaking observed near the epicenter of the earthquake, categorized by various seismic intensity scales such as the rossiforel scale. Seismic design practices and response analyses of infrastructures have conventionally used peak ground acceleration pga, velocity pgv, displacement pgd or spectral intensities such as spectral acceleration sa and displacement sd as an. The largest earthquake ever recorded on earth was a magnitude 9. What is the difference between magnitude and intensity. Based on human reactions, natural objects and manmade structures, the mercalli scale rates earthquakes on a scale of 1 to 12, with 1 denoting that nothing was felt and 12 denoting total destruction. Mar 16, 2011 the largest earthquake ever recorded on earth was a magnitude 9. Nov 17, 2016 the richter magnitude scale was developed in 1935 by charles f. Performancebased earthquake engineering, ground motion intensity measures abstract. The magnitude of earthquake is determined from measurements on seismographs, whereas the intensity. The richter magnitude scale measures the amount of seismic energy released by an earthquake when an earthquake occurs, its magnitude can be given a single numerical. Magnitude is determined from measurements on seismographs. The circle sizes correspond to earthquake magnitude, ranging from 4. Well for measuring the intensitymagnitude of an earthquake we usually use mercallis intensity scale. Magnitudes are usually determined from measurements of an earthquakes seismic waves as recorded on a seismogram.

Richter 1935 defined the local magnitude ml of an earthquake observed. The usefulness of earthquake intensity in seismic hazard estimation carries over into seismic risk studies in very similar ways. The duration of an earthquake is related to its magnitude but not in a perfectly strict sense. How the richter scale measures earthquakes be prepared. The richter magnitude scale was developed in 1935 by charles f. In may 1997, jabalpur madhya pradesh suffered an earthquake of magnitude 6. With ventura in the middle of an earthquake swarm, learn about the differences between magnitude and intensity. So, for example, a magnitude 2 earthquake is 31 times more powerful than a magnitude 1 earthquake. Magnitude the magnitude is a number that characterizes the relative size of an earthquake. Magnitude measures the energy released at the source of the earthquake.

Often, several slightly different magnitudes are reported for an earthquake. Magnitude also affects intensity, since an earthquake of a higher magnitude has a higher intensity than an earthquake of lower magnitude. Why are some earthquakes more destructive than others. When this stress becomes great enough to rupture the crust, or to overcome the friction that prevents one block of crust from slipping past another, energy is released, some of it in the form of various kinds of seismic waves that cause groundshaking, or quaking. Richter of the california institute of technology as a mathematical device to compare the size of earthquakes. This scale worked fairly well as far as it went, which was for small and moderate earthquakes in southern california. Jan 14, 2020 to test his theory, song looked back at three historic events. Magnitude and intensity measure different characteristics of earthquakes. Earthquake size is a quantitative measure of the size of the earthquake at its source. Whereas higher magnitude earthquakes havegreater energyrelease andcanpotentially affectamuchlargerarea,lossesdependdirectly on the exposure and vulnerability of a population to specific levels of shaking. Part of the confusion probably arises from the general similarity of scales used express these quantities. Part of the confusion probably arises from the general. Measures the earthquakes strength based on the size of the area of the fault that moves, and the rigidity of the rocks in the fault. Magnitude scales, like the moment magnitude, measure the size of the earthquake at its source.

Neither earthquake magnitude nor macroseismic intensity provides sufficient information to judge the overall impact of an earthquake. The former measures the energy released at the source of the earthquake. The mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake. Below is shown the distanceamplitude relationship for earthquakes. The moment magnitude scale is often referred to by the name of its predecessor, the richter scale. Intensity measures and observed damages this study presents several seismic acceleration parameters of the athens earthquake main shock, along with a statistical analysis of them. How is an earthquake measured there are two numbers generally measured, whenever an earthquake occurs its magnitude and intensity.

The richter scale measures the magnitude of an earthquake how powerful it is. It measures the effects of an earthquake, and is distinct from the moment magnitude usually reported for an earthquake sometimes misreported as the richter magnitude, which is a measure of the energy released. It is very common to confuse between the two commonly used measures of an earthquake intensity and magnitude. The amount of ground motion is one measure of earthquake intensity. For weak earthquakes we usally use a manner in which the earthquake is felt by people as a measure. In many instances, the two terms are erroneously used interchangeably. Size is used in the sense of the quantity of energy. A magnitude scale measures the force or energy of an earthquake, but an intensity scale measures the level of shaking which occurs at an observation point on the earths surface. Comparison between measurements on the modified mercalli scale and magnitudes on the moment magnitude scale. Difference between earthquake magnitude and intensity. Moment magnitude is the best single measure of the total energy released, i. Intensity and intensity scales gfzpublic gfzpotsdam.

Pdf intensity measures for response prediction of a. 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. In general, only if the earthquake magnitude reaches above 6. The magnitude do not depend on where the measurement is made. Magnitudeintensity pacific northwest seismic network. The biggest earthquake whose magnitude we know was in 1960, in the pacific right off central chile on may 22. Measures the earthquake s strength based on the size of the area of the fault that moves, and the rigidity of the rocks in the fault. What are the control measures for earthquakes answers. It is one of the service agencies of the department of science and technology. Mathematically, an earthquake of magnitude x results in seismic waves with amplitudes proportional to 10x. Richter and presented in his landmark 1935 paper, where he called it the magnitude scale.

Intensity of an earthquake is a measure of its effect, i. But, an earthquake in a densely populated area that results in many deaths and considerable damage high intensity may have the same magnitude as an earthquake in a remote area that does no more. Seismic magnitude scales are used to describe the overall strength or size of an earthquake. The richter magnitude scale measures the amount of seismic. In the analysis of earthquake tsunami we usually use the moment magnitude m w. Because of various shortcomings of the m l scale most. Intensity measures the strength of shaking produced by the earthquake at a certain location.

The severity of earthquake shaking is assessed using a descriptive scale the modified mercalli intensity scale. It now supersedes the richter magnitude scale which measures the height of a seismic wave. Thus it is clear that magnitude is a fixed value independent of distance from the epicenter of the earthquake, whereas intensity varies and is measured differently at different places depending upon its distance from the epicenter. All magnitude scales should yield approximately the same value for any given earthquake. The mercalli scale measures the intensity of an earthquake by quantifying the effects of an earthquake on the earths surface. While magnitude is termed as the strength of the earthquake, the intensity of the natural calamity varies from place to place, depending upon a number of factors. Intensity decreases as we move farther from the epicenter. For calculating intensity, the responses of people.

The earthquake size is usually expressed as the earthquake magnitude and intensity. The moment magnitude scale measures the overall magnitude or size of the earthquake, and the modified mercalli scale measures earthquake. Pdf the effects of earthquake significant duration d595. It is measured using a machine called a seismometer which produces a seismograph. What happened in the meantime was that tom hanks and hiroo kanamori came up with a better magnitude scale in 1979. However, it can be considered to be even more useful, since seismic risk studies are concerned with establishing the probability of damage or loss occurring, and intensity is a direct. Measures of an earthquake, magnitude and intensity measures.

The two scales will indicate similar results if the earthquake magnitudes are between 3. Body wave magnitude is a similar concept, but applied usually to teleseisms earthquake more than 3000 km from the recording station and good for deep and. In the framework of performancebased assessment of existing rc buildings, an important step is the definition of an intensity measure im of the seismic action that be accurate and efficient in correlating with the engineering demand parameters. Measurements on the modified mercalli intensity mmi scale range from i to xii and are based solely on damage assessment and eyewitness accounts. Intensity is the quantum of negative impact of earthquake on surrounding areas. A is 10x more intense than b a is more intense than b richter magnitude does not measure intensity b is 0. The magnitude of an earthquake is determined from the logarithm of the a. Although magnitude and intensity are basically different measures of an earthquake, they are frequently confused by the public and new reports of earthquakes. Magnitude and intensity measure various characteristics of earthquake. It is very common to confuse between the two commonly used measures of an earthquakeintensity and magnitude.

Magnitude is based on measurement of the maximum motion recorded by a seismograph4. This happens because the relation between the seismic measurements and the magnitude is complex and different. However, the latter measures the strength of shaking generated by the earthquake at a certain location. To prevent anearthquake hazard the building should be properly designed. The higher numbers of the scale are based on observed structural damage. Three of the most common measures of earthquakes are movement magnitude, modified mercalli intensity mmi scale and acceleration. The magnitude of early earthquakes can be assessed from the intensity distribution and reported fault displacement, leading to enhanced data for parameters for the design of earthquakeresistant. Unlike magnitude, the intensity that is the devastation caused by earthquake varies with the location and is not a single numerical value. Intensity is a crude measure of earthquake size based on indirect, subjective descriptions, such as how strongly people reacted and the type and extent of building. Mar 12, 2011 difference between earthquake magnitude and intensity. Shortcomings of intensity scales not directly related to earthquake source damage obviously distancedependent needs population to report damage affected by site response example of intensity maps for 1886 charleston, usa, earthquake. The richter scale also called the richter magnitude scale or richters magnitude scale is a measure of the strength of earthquakes, developed by charles f. The actual seismicwave amplitude at a particular site. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking quaking caused by an earthquake at a given location.