For example, an earthquake intense enough to be felt by a person standing nearby is said to have an intensity of mm iii. Modified mercalli intensity scale which shows ground. Intensity distribution and isoseismal maps for the northridge, california, earthquake of january 17,1994, usgs openfile report 9592. The modified mercalli intensity or mmi was based in part on postal questionnaires, in which respondents summarize the effects of shaking in their communities. Modified mercalli intensity scale of 1931 the formation of. The modified mercalli intensity scale mm or mmi, descended from giuseppe mercalli s mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. Intensity, that is, the rather ambiguous expressions of shaking. Mercalli intensity value modified mercalli intensity scale description peak ground acceleration % g i. The mercalli intensity scale is a seismic scale uised for measurin the intensity o an yirdquauk. Relationship between modified mercalli intensity and peak. The mercalli intensity scale or more precisely the modified mercalli intensity scale is a scale to measure the intensity of earthquakes.
Modified mercalli intensity scale value description. The modified mercalli intensity scale has been used to categorise noninstrumental observations of earthquakes in new zealand since the mid1940s when it replaced the rossiforel scale then in use. Davison, charles june 1921, on scales of seismic intensity and on the construction and use of. The one currently used in the united states is the modified mercalli mm intensity scale. It was developed in 1931 by the american seismologists harry wood and frank neumann. What is the difference between magnitude and intensity. The cities kodiak and anchorage are shown on the map. The map shows modified mercalli intensity scale damage zones resulting from a large earthquake that occurred in 1964. The modified mercalli intensity scale is a semiquantitative linear scale developed in 1931 by the american seismologists harry wood and frank neumann. Modified mercalli scale uwi seismic research centre.
Modified mercalli intensities for nine earthquakes in central and. Instrumental not felt except by a very few under especially favorable conditions. Be sure you have an application to open this file type before downloading. Intensity scales, like the modified mercalli scale and the rossiforel scale, measure the amount of shaking at a particular location. Modified mercalli intensity scale of 1931, as originally abridged by wood and neumann. Although numerous intensity scales have been developed over the last several hundred years, the one currently used in the united states is the modified mercalli intensity scale, mmi, developed in 1931 by harry wood and frank neumann. It measures the shaking you feel during an earthquake. Helps students understnad difference between magnitude and intensity. Unlike with the richter scale, the mercalli scale does not take into account energy of an earthquake directly. Mercalli scale illustrated activity teachengineering.
It measures the effects of an earthquake at a given location, distinguished from the earthquakes inherent force or strength as measured by. The modified mercalli intensity scale simplified, from reference. Ask students to use their labeled wattsville map with scale roman numerals, rings and write an explanation of how caller descriptions can be used to identify where an earthquake originates. Magnitude and intensity measure different characteristics of earthquakes. Pdf the modified mercalli intensity scale revisions arising from. In santa clara county aresraces, we use the modified mercalli intensity scale for. In new zealand, where earthquakes occur from near the surface right down to a depth of over 600 km, the modified mercalli intensity scale is a better indicator of an earthquakes effects on.
Mercalli intensity scale synonyms, mercalli intensity scale pronunciation, mercalli intensity scale translation, english dictionary definition of. The earthquakes epicenter was near anchorage, alaska. Mercalli intensity scale modified mercalli intensity scale which shows ground accelerations by intensity level. Mercalli intensity scale simple english wikipedia, the. It measures the effects of an earthquake at a given location, distinguished from the earthquakes inherent force or strength as measured by seismic magnitude scales such as the. Pdf modified mercalli intensities for nine earthquakes. The relationship between richter magnitude and modified. The table below shows approximately how many earthquakes occur each year in each magnitude range and what the intensity might be at the epicenter for each magnitude range. Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. Pdf the modified mercalli intensity scale revisions. Modified mercalli scale how is modified mercalli scale. If this table is garbled, try the plain text version. It measurs the effects o an yirdquauk, an is distinct frae the moment magnitude uisually reportit for an yirdquauk whiles misreportit as the richter magnitude, which is a measur o the energy released.
This was later revised and renamed the local magnitude scale, denoted as ml or m l. Instead of using vague and subjective descriptions like major, minor or heavy, a mikemike value is reported. 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. Modified mercalli scale intensity effects pgagals i not felt. Modified mercalli intensity scale for additional information on statistics on percentage of uninhabitable residential units by construction type and mmi level, click here. The 1906 earthquake was so large that the shaking effects do not fit richters 1958 modified mercalli intensity scale.
So the intensity of an earthquake will vary depending on where you are. Modified mercalli intensities for nine earthquakes in. The intensity of an earthquake is listed along with effects on the modified mercalli scale in this printable guide. A revision of the modified mercalli intensity scale eqc. We will now try to relate the intensity to acceleration.
Modified mercalli intensity how is modified mercalli intensity abbreviated. The modified mercalli intensity scale mm or mmi, descended from giuseppe mercallis mercalli intensity scale of 1902, is a seismic intensity scale used for measuring the intensity of shaking produced by an earthquake. We have developed regression relationships between modified mercalli intensity imm and peak ground acceleration pga and velocity pgv by comparing horizontal peak ground motions to observed intensities for eight significant california earthquakes. We determine modified mercalli seismic intensities mmi for nine onshore earthquakes of magnitude 4.
For the limited range of modified mercalli intensities imm, we find that for peak acceleration with v. Some intensity scales in the past, such as the modified mercalli scale in its 1956. Modifiedmercalliintensityscale earthquakedamagereporting byjohnjacobschmidt,amrron intheimmediateaftermathofanearthquake,searchandrecoveryeffortswill. This caveat, of course, naturally follows the historic development of modified mercalli. Although numerous intensity scales have been developed over the last several hundred years to evaluate the effects of earthquakes, the one currently used in the united states is the modified mercalli mm intensity scale. Modified mercalli intensity scale wikimili, the free.
Handout primarily discussing the modified mercalli scale. The mercalli scale uses human observation to assess damage from an earthquake, while a richter scale uses instruments to measure how much force an earthquake produces, or the size of its waves. The intensity of the earthquakes is valued according to the richter scale charles francis richter 2641900 3091985 or the modified mercalli scale giuseppe mercalli 2151850 1931914. The intensity o an yirdquauk is nae tot determined bi its magnitude. Modified mercalli intensity scale of 1931 bulletin of. Science briefs about new earthquake research written for nonscientists. Revisions in this version of the scale are shown in italics. The mercalli scale is a rather arbitrary set of definitions based upon what people in the area feel, and their observations of damage to buildings around them. We enumerate the characteristic effects observed in the 1906 earthquake and discuss how the mmi intensity scale was revised for this earthquake. This scale ranks the shaking levels in an ascending order from i to xii. Richter famous from the richter scale gives an empirical formula.
Marginal and longperiod effects of large earthquakes. Mmi value description of shaking severity summary damage description used on 1995 maps full description i. Review the roman numerals and read their descriptions. 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. Maps for the northridge, california, earthquake of january 17, 1994 pdf, u. The first scale furnishes an evaluation magnitude of the quantity of freed energy, while the seconds scale assigns a degree to the effects on the. The most widely used intensity scale, the modified mercalli scale, is divided into 12 degrees, each identified by a roman numeral. The strength of an earthquake is usually measured on one of two scales, the modified mercalli scale and the richter scale. Fun and educational resources including science fair ideas and earthquake science you can understand.
Display the modified mercalli scale on the overhead projector. Magnitude measures the energy released at the source of the. An earthquake causes many different intensities of shaking in the area of the epicenter where it occurs. This scale is composed of 12 increasing levels of intensity, designated by roman numerals, ranging from imperceptible shaking to catastrophic destruction. The modified mercalli intensity scale san diego county. Rather, they classify earthquakes by the effects they have and the destruction they cause. This scale features 12 increasing levels of intensity, ranging from minor shaking to catastrophic destruction and shows its increments in roman numerals. For united states earthquakes, intensities are assigned on the basis of the modified mercalli intensity mmi scale wood and neumann, 1931. This value is quick and simple to communicate over the air and equates to an objective. Today, we are going to look at the mercalli scales damage rating and create a booklet to help inform citizens of potential danger.
The lower numbers of the intensity scale generally deal with the manner in which the earthquake is felt. The modified mercalli intensity scale mm or mmi, descended from giuseppe mercallis. The predominant vulnerable building types are unreinforced brick masonry and reinforced masonry construction. Empirical means that richter took many earthquakes for which intensities were observed at locations where acceleration. Usgs resources and links to outside educational resources. As you can see here, as the numbers get higher, the more you feel the shaking. Modified mercalli intensity how is modified mercalli. Base your answer to the following question on the map and the modified mercalli intensity scale below. Pdf recent studies of the effects and modified mercalli mm intensities of new zealand earthquakes have established criteria that will. Richter and presented in his landmark 1935 paper, where he called it the magnitude scale.
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