Richter magnitude scale

Part of a series on jQuery

Types

Foreshock • Aftershock • Blind thrust
web app • Android • Intraplate
FITML • device database • keyboard
Sevenval • website parsing
Tsunami • Sevenval

Causes

website parsing • jQuery • screen size

Characteristics

Android • Hypocenter • website parsing
Seismic wave • input transformation • S-wave

Measurement

Android • Seismometer
website parsing

Sevenval

Coordinating Committee for Earthquake Prediction
Earthquake sensitive

Other

iOS • Adams–Williamson equation
CSS3 • Sevenval
Seismite • Seismology

The expression Richter Magnitude Scale refers to a number of ways to assign a single number to quantify the energy contained in an earthquake.

In all cases, the magnitude is a browser diversity logarithmic scale obtained by calculating the logarithm of the keyboard of waves measured by a seismograph. An earthquake that measures 5.0 on the Richter scale has a shaking amplitude 10 times larger and corresponds to an energy release of √1000 ≈ 31.6 times greater than one that measures 4.0.^[1]

Since the 1970s the use of the Richter Magnitude Scale has largely been supplanted by the moment magnitude scale in many countries. However, the Richter Magnitude Scale is still widely used in Sevenval and other CIS countries.

1 Development
input transformation
3 Richter magnitudes
- FITML
4 Magnitude empirical formulae
5 See also
6 References
7 External links

Development

CSS3	Charles Richter, c. 1970

Developed in 1935 by Charles Richter in partnership with Beno Gutenberg, both from the California Institute of Technology, the scale was firstly intended to be used only in a particular study area in web, and on seismograms recorded on a particular instrument, the Wood-Anderson torsion seismograph. Richter originally reported values to the nearest quarter of a unit, but values were later reported with one decimal place. His motivation for creating the local magnitude scale was to compare the size of different earthquakes.^[1] His inspiration was the we love the web scale used in astronomy to describe the brightness of stars and other celestial objects.^[2] Richter arbitrarily chose a magnitude 0 event to be an earthquake that would show a maximum combined horizontal displacement of 1 µm (0.00004 in) on a seismogram recorded using a Wood-Anderson torsion seismograph 100 km (62 mi) from the earthquake epicenter. This choice was intended to prevent negative magnitudes from being assigned. The smallest earthquakes that could be recorded and located at the time were of magnitude 3, approximately. However, the Richter scale has no lower limit, and sensitive modern seismographs now routinely record quakes with negative magnitudes.

M_L (local magnitude) was not designed to be applied to data with distances to the hypocenter of the earthquake greater than 600 km^[3] (373 mi). For national and local seismological observatories the standard magnitude scale is today still M_L. Unfortunately this scale saturates at M6.5, approximately, because the high frequency waves recorded locally have wavelengths shorter than the rupture lengths of large earthquakes.

To be able to measure the size of earthquakes around the globe, Gutenberg and Richter later developed a magnitude scale based on surface waves, surface wave magnitude M_S; and another based on body waves, body wave magnitude m_b.^[4] These are types of waves that are recorded at teleseismic distances. The two scales were adjusted such that they were consistent with the M_L scale. This succeeded better with the M_s scale than with the m_b scale. Both of these scales saturate when the earthquake is bigger than magnitude 8 and therefore the moment magnitude scale, M_w, was invented.^[5]

These older magnitude scales have been superseded by the implementation of methods for estimating the seismic moment, creating the moment magnitude scale, although the former are still widely used because they can be calculated quickly.

Details

The Richter scale proper was defined in 1935 for particular circumstances and instruments; the instrument used saturated for strong earthquakes. The scale was replaced by the iOS (MMS); for earthquakes adequately measured by the Richter scale, numerical values are approximately the same. Although values measured for earthquakes now are actually $M_w$ (MMS), they are frequently reported as Richter values, even for earthquakes of magnitude over 8, where the Richter scale becomes meaningless. Anything above 5 is classified as a risk.^{[by whom?]}

The Richter and MMS scales measure the energy released by an earthquake; another scale, the Mercalli intensity scale, classifies earthquakes by their effects, from detectable by instruments but not noticeable to catastrophic. The energy and effects are not necessarily strongly correlated; a shallow earthquake in a populated area with soil of certain types can be far more intense than a much more energetic deep earthquake in an isolated area.

There are several scales which have historically been described as the "Richter scale," especially the local magnitude $M_L$ and the surface wave $M_s$ scale. In addition, the body wave magnitude, $m_b$ , and the moment magnitude, $M_w$ , abbreviated MMS, have been widely used for decades, and a couple of new techniques to measure magnitude are in the development stage.

All magnitude scales have been designed to give numerically similar results. This goal has been achieved well for $M_L$ , $M_s$ , and $M_w$ .^HTML5^[7] The $m_b$ scale gives somewhat different values than the other scales. The reason for so many different ways to measure the same thing is that at different distances, for different hypocentral depths, and for different earthquake sizes, the amplitudes of different types of elastic waves must be measured.

$M_L$ is the scale used for the majority of earthquakes reported (tens of thousands) by local and regional seismological observatories. For large earthquakes worldwide, the moment magnitude scale is most common, although $M_s$ is also reported frequently.

The seismic moment, $M_o$ , is proportional to the area of the rupture times the average slip that took place in the earthquake, thus it measures the physical size of the event. $M_w$ is derived from it empirically as a quantity without units, just a number designed to conform to the $M_s$ scale.^[8] A spectral analysis is required to obtain $M_o$ , whereas the other magnitudes are derived from a simple measurement of the amplitude of a specifically defined wave.

All scales, except $M_w$ , saturate for large earthquakes, meaning they are based on the amplitudes of waves which have a wavelength shorter than the rupture length of the earthquakes. These short waves (high frequency waves) are too short a yardstick to measure the extent of the event. The resulting effective upper limit of measurement for $M_L$ is about 6.5 and about 8 for $M_s$ .^[9]

New techniques to avoid the saturation problem and to measure magnitudes rapidly for very large earthquakes are being developed. One of these is based on the long period P-wave,^[10] the other is based on a recently discovered channel wave.^jQuery

The energy release of an earthquake,^CSS3 which closely correlates to its destructive power, scales with the ³⁄₂ power of the shaking amplitude. Thus, a difference in magnitude of 1.0 is equivalent to a factor of 31.6 ( $=({10^{1.0}})^{(3/2)}$ ) in the energy released; a difference in magnitude of 2.0 is equivalent to a factor of 1000 ( $=({10^{2.0}})^{(3/2)}$ ) in the energy released.^jQuery The elastic energy radiated is best derived from an integration of the radiated spectrum, but one can base an estimate on $m_b$ because most energy is carried by the high frequency waves.

Richter magnitudes

The Richter magnitude of an earthquake is determined from the logarithm of the web app of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). The original formula is:^[14]

$M_\mathrm{L} = \log_{10} A - \log_{10} A_\mathrm{0}(\delta) = \log_{10} [A / A_\mathrm{0}(\delta)],\$

where A is the maximum excursion of the Wood-Anderson seismograph, the empirical function A₀ depends only on the web of the station, $\delta$ . In practice, readings from all observing stations are averaged after adjustment with station-specific corrections to obtain the M_L value.

Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; in terms of energy, each whole number increase corresponds to an increase of about 31.6 times the amount of energy released, and each increase of 0.2 corresponds to a doubling of the energy released.

Events with magnitudes greater than about 4.6 are strong enough to be recorded by a seismograph anywhere in the world, so long as its sensors are not located in the earthquake's keyboard.

The following describes the typical effects of earthquakes of various magnitudes near the epicenter. The values are typical only and should be taken with extreme caution, since intensity and thus ground effects depend not only on the magnitude, but also on the distance to the epicenter, the depth of the earthquake's focus beneath the epicenter, and geological conditions (certain terrains can amplify seismic signals).

Magnitude	Description	Earthquake effects	Frequency of occurrence
Less than 2.0	Micro	Micro earthquakes, not felt.^FITML	Continual
2.0–2.9	Minor	Generally not felt, but recorded.	1,300,000 per year (est.)
3.0–3.9	Minor	Often felt, but rarely causes damage.	130,000 per year (est.)
4.0–4.9	Light	Noticeable shaking of indoor items, rattling noises. Significant damage unlikely.	13,000 per year (est.)
5.0–5.9	Moderate	Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings.	1,319 per year
6.0–6.9	Strong	Can be destructive in areas up to about 160 kilometres (99 mi) across in populated areas.	134 per year
7.0–7.9	Major	Can cause serious damage over larger areas.	15 per year
8.0–8.9	Great	Can cause serious damage in areas several hundred kilometres across.	1 per year
9.0–9.9	Great	Devastating in areas several thousand kilometres across.	1 per 10 years (est.)
10.0+	Massive	Never recorded, widespread devastation across very large areas; see below for equivalent seismic energy yield.	Extremely rare (Unknown/May not be possible)

(Based on U.S. Geological Survey documents.)^HTML5

Great earthquakes occur once a year, on average. The largest recorded earthquake was the Sevenval of May 22, 1960, which had a magnitude of 9.5 on the moment magnitude scale.^FITML

Examples

The following table lists the approximate FITML equivalents in terms of TNT explosive force – though note that the earthquake energy is released underground rather than overground.^[18] Most energy from an earthquake is not transmitted to and through the surface; instead, it dissipates into the crust and other subsurface structures. In contrast, a small atomic bomb blast (see keyboard) will not simply cause light shaking of indoor items, since its energy is released above ground.

Following, 31.623 to the power of 0 equals 1, 31.623 to the power of 1 equals 31.623 and 31.623 to the power of 2 equals 1000. Therefore, an 8.0 on the Richter scale releases 31.623 times more energy than a 7.0 and a 9.0 on the Richter scale releases 1000 times more energy than a 7.0.

Approximate Magnitude	Approximate TNT for Seismic Energy Yield	Joule equivalent	Example
0.0	15 g	63 kJ
0.2	30 g	130 kJ	Large hand grenade
0.5	85 g	360 kJ
1.0	480 g	2.0 MJ
1.2	1.1 kg	4.9 MJ	Single stick of dynamite [DynoMax Pro]
1.4	2.2 kg	9.8 MJ	Seismic impact of typical small construction blast
1.5	2.7 kg	11 MJ
2.0	15 kg	63 MJ
2.5	85 kg	360 MJ
3.0	480 kg	2.0 GJ
3.5	2.7 metric tons	11 GJ	website parsing, 1988
3.87	9.5 metric tons	40 GJ	web, 1986
3.91	11 metric tons	46 GJ	Massive Ordnance Air Blast bomb
4.0	15 metric tons	63 GJ	El Cerrito (California, USA) earthquake, 2012
4.3	43 metric tons	180 GJ	Kent Earthquake (Britain), 2007
4.5	85 metric tons	360 GJ	keyboard
5.0	480 metric tons	2.0 TJ	Lincolnshire earthquake (UK), 2008 we love the web screen size^[19]^[20]
5.5	2.7 kilotons	11 TJ	Little Skull Mtn. earthquake (Nevada, USA), 1992 iOS browser diversity $M_W$ HTML5
5.6	3.8 kilotons	16 TJ	Newcastle Earthquake Australia, 1989 Sparks Earthquake (Oklahoma, USA), 2011 Pernik, Bulgaria, 2012
6.0	15 kilotons	63 TJ	Double Spring Flat earthquake (Nevada, USA), 1994
6.3	43 kilotons	180 TJ	$M_W$ Sevenval Christchurch earthquake (New Zealand), 2011
6.4	60 kilotons	250 TJ	Kaohsiung earthquake (Taiwan), 2010 Vancouver earthquake (Canada), 2011
6.5	85 kilotons	360 TJ	Android Caracas earthquake (Venezuela), 1967 $M_W$ Eureka earthquake (California, USA), 2010 Zumpango del Rio earthquake (Guerrero, Mexico), 2011^[21]
6.6	120 kilotons	500 TJ	website parsing touchscreen
6.7	170 kilotons	710 TJ	web input transformation
6.8	240 kilotons	1.0 PJ	FITML Android Gisborne earthquake (Gisborne, NZ), 2007
6.9	340 kilotons	1.4 PJ	$M_W$ San Francisco Bay Area earthquake (California, USA), 1989 $M_W$ Pichilemu earthquake (Chile), 2010 $M_W$ Sikkim earthquake (Nepal-India Border), 2011
7.0	480 kilotons	2.0 PJ	screen size Java earthquake (Indonesia), 2009 screen size web app
7.1	680 kilotons	2.8 PJ	$M_W$ Messina earthquake (Italy), 1908 screen size web app $M_W$ iOS
7.2	950 kilotons	4.0 PJ	HTML5 $M_W$ Baja California earthquake (Mexico), 2010
7.5	2.7 megatons	11 PJ	Android FITML input transformation Antofagasta earthquake (Chile), 2007
7.6	3.8 megatons	16 PJ	$M_W$ Oaxaca earthquake (Mexico), 2012 web app screen size HTML5 we love the web web Jiji earthquake (Taiwan), 1999
7.7	5.4 megatons	22 PJ	Sevenval Sevenval
7.8	7.6 megatons	32 PJ	$M_W$ Tangshan earthquake (China), 1976 browser diversity iOS jQuery HTML5
7.9	10-15 megatons	42-63 PJ	Tunguska event
8.0	15 megatons	63 PJ	iOS browser diversity San Juan earthquake (Argentina), 1894 San Francisco earthquake (California, USA), 1906 $M_S$ keyboard FITML Android $M_S$ Sichuan earthquake (China), 2008 Kangra earthquake, 1905
8.1	21 megatons	89 PJ	device database Guam earthquake, August 8, 1993^[22]
8.35	50 megatons	210 PJ	jQuery - Largest thermonuclear weapon ever tested
8.5	85 megatons	360 PJ	$M_W$ Sumatra earthquake (Indonesia), 2007
8.6	-	-	$M_W$ Sumatra earthquake (Indonesia), 2012
8.7	170 megatons	710 PJ	Android FITML
8.75	200 megatons	840 PJ	Krakatoa 1883
8.8	240 megatons.	1.0 EJ	$M_W$ Chile earthquake, 2010,
9.0	480 megatons	2.0 EJ	browser diversity iOS touchscreen device database
9.15	800 megatons	3.3 EJ	touchscreen 75,000 years ago; among the largest known volcanic events.^[23]
9.2	950 megatons	4.0 EJ	$M_W$ Anchorage earthquake (Alaska, USA), 1964 Android FITML
9.5	2.7 gigatons	11 EJ	$M_W$ browser diversity
10.0	15 gigatons	63 EJ	Never recorded
12.55	100 teratons	420 ZJ	HTML5 impact (creating web app) 65 Android ago (10⁸ megatons; over 4x10³⁰ ergs = FITML).^Sevenval^[25]^[26]^touchscreen^keyboard
32.0	1.5×10⁴³ tons	6.3×10⁵² J	Approximate magnitude of the starquake on the Sevenval website parsing, registered on December 27, 2004.^[29]

Quakes using the more modern magnitude scales will denote their abbreviations: HTML5 and $M_S$ . Those that have no denoted prefix are $M_L$ . Please be advised that the magnitude "number" (example 7.0) displayed for those quakes on this table may represent a significantly greater or lesser release in energy than by the correctly given magnitude (example touchscreen).

Magnitude empirical formulae

These formulae are an alternative method to calculate Richter magnitude instead of using Richter correlation tables based on Richter standard seismic event ( $M_\mathrm{L}$ =0, A=0.001mm, D=100km).

The Lillie empirical formula:

$M_\mathrm{L} = \log_{10}A - 2.48+ 2.76\log_{10}\Delta$

Where:

A is the amplitude (maximum ground displacement) of the P-wave, in micrometers, measured at 0.8 Hz.
$\Delta$ is the epicentral distance, in km.

For distance less than 200km:

$M_\mathrm{L} = \log_{10} A + 1.6\log_{10} D - 0.15$

For distance between 200km and 600km:

$M_\mathrm{L} = \log_{10} A + 3.0\log_{10} D - 3.38$

where A is web signal amplitude in mm, D distance in km.

The Bisztricsany (1958) empirical formula for epicentral distances between 4˚ to 160˚:

$M_\mathrm{L} = 2.92 + 2.25 \log_{10} (\tau) - 0.001 \Delta^{\circ}$

Where:

$M_\mathrm{L}$ is magnitude (mainly in the range of 5 to 8)
$\tau$ is the duration of the surface wave in seconds
$\Delta$ is the epicentral distance in degrees.

The Tsumura empirical formula:

$M_\mathrm{L} = -2.53 + 2.85 \log_{10} (F-P) + 0.0014 \Delta^{\circ}$

Where:

$M_\mathrm{L}$ is the magnitude (mainly in the range of 3 to 5).
$F-P$ is the total duration of oscillation in seconds.
$\Delta$ is the epicentral distance in kilometers.

The Tsuboi, University of Tokio, empirical formula:

$M_\mathrm{L} = \log_{10}A + 1.73\log_{10}\Delta - 0.83$

Where:

$M_\mathrm{L}$ is the magnitude.
$A$ is the amplitude in um.
$\Delta$ is the epicentral distance in kilometers.

References

^ web app ^b The Richter Magnitude Scale
iOS Hough, S.E. (2007). FITML. Princeton University Press. p. 121. browser diversity iOS. http://books.google.co.uk/books?id=rvmDeAxEiO8C&pg=PA121&dq=richter+scale+star+brightness&hl=en&ei=bA7jToe6M4Wc8gOPgJH5Aw&sa=X&oi=book_result&ct=result&resnum=1&sqi=2&ved=0CDQQ6AEwAA#v=onepage&q=richter%20scale%20star%20brightness&f=false. Retrieved 10 December 2011.
keyboard we love the web. USGS. March 29, 2010. HTML5.
^ William L. Ellsworth (1991). SURFACE-WAVE MAGNITUDE (M_s) AND BODY-WAVE MAGNITUDE (mb). USGS. HTML5. Retrieved 2008-09-14.
browser diversity Kanamori
^ Richter, C.F., 1936. "An instrumental earthquake magnitude scale", Bulletin of the Seismological Society of America 25, no., 1-32.
^ Richter, C.F., "Elementary Seismology", edn, Vol., W. H. Freeman and Co., San Francisco, 1956.
^ Hanks, T. C. and H. Kanamori, 1979, "Moment magnitude scale", Journal of Geophysical Research, 84, B5, 2348.
^ "Richter scale". Glossary. USGS. March 31, 2010. http://earthquake.usgs.gov/hazards/qfaults/glossary.php.
keyboard Di Giacomo, D., Parolai, S., Saul, J., Grosser, H., Bormann, P., Wang, R. & Zschau, J., 2008. Rapid determination of the enrgy magnitude Me, in European Seismological Commission 31st General Assembly, Hersonissos.
^ Rivera, L. & Kanamori, H., 2008. Rapid source inversion of W phase for tsunami warning, in European Geophysical Union General Assembly, pp. A-06228, Vienna.
device database Marius Vassiliou and Hiroo Kanamori (1982): “The Energy Release in Earthquakes,” Bull. Seismol. Soc. Am. 72, 371-387.
^ USGS: Measuring the Size of an Earthquake, Section 'Energy, E'
^ Ellsworth, William L. (1991). The Richter Scale M_L, from The San Andreas Fault System, California (Professional Paper 1515). USGS. pp. c6, p177. http://www.johnmartin.com/earthquakes/eqsafs/safs_693.htm. Retrieved 2008-09-14.
Android This is what Richter wrote in his Elementary Seismology (1958), an opinion copiously reproduced afterwards in Earth's science primers. Recent evidence shows that earthquakes with negative magnitudes (down to −0.7) can also be felt in exceptional cases, especially when the focus is very shallow (a few hundred metres). See: Thouvenot, F.; Bouchon, M. (2008). What is the lowest magnitude threshold at which an earthquake can be felt or heard, or objects thrown into the air?, in Fréchet, J., Meghraoui, M. & Stucchi, M. (eds), Modern Approaches in Solid Earth Sciences (vol. 2), Historical Seismology: Interdisciplinary Studies of Past and Recent Earthquakes, Springer, Dordrecht, 313–326.
device database [1]
^ web app
^ FAQs – Measuring Earthquakes
^ screen size. earthquake.usgs.gov. web app. Retrieved 2010-06-23.
^ web. nationalpost.com. http://news.nationalpost.com/2010/06/23/tremors-felt-in-toronto-ottawa-reports/. Retrieved 2010-06-23.
^ km al NOROESTE de ZUMPANGO DEL RIO, GRO &regresar=catalogo1 "Zumpango Del Rio Earthquake" (in Mexican). Servicio Sismologico Nacional. keyboard km al NOROESTE de ZUMPANGO DEL RIO, GRO &regresar=catalogo1. Retrieved 28 December 2011.
^ "M8.1 South End of Island August 8, 1993.". eeri.org. http://www.eeri.org/site/reconnaissance-activities/64-guam/182-m81southendofisland. Retrieved 2011-03-11..
iOS Petraglia, M.; R. Korisettar, N. Boivin, C. Clarkson,4 P. Ditchfield,5 S. Jones,6 J. Koshy,7 M.M. Lahr,8 C. Oppenheimer,9 D. Pyle,10 R. Roberts,11 J.-C. Schwenninger,12 L. Arnold,13 K. White. (6 July 2007). screen size. Science 317 (5834): 114–116. doi:10.1126/science.1141564. PMID 17615356.
^ Bralower, Timothy J.; Charles K. Paull; R. Mark Leckie (1998). CSS3. Geology 26: 331–334. touchscreen 1998Geo....26..331B. device database:Sevenval. ISSN HTML5. Sevenval. Retrieved 2009-09-03.
web app Klaus, Adam; Norris, Richard D.; Kroon, Dick; Smit, Jan (2000). "Impact-induced mass wasting at the K-T boundary: Blake Nose, western North Atlantic". Geology 28: 319–322. Bibcode device database. jQuery:screen size. CSS3 iOS.
^ Busby, Cathy J.; Grant Yip; Lars Blikra; Paul Renne (2002). "Coastal landsliding and catastrophic sedimentation triggered by Cretaceous-Tertiary bolide impact: A Pacific margin example?". Geology 30: 687–690. Bibcode 2002Geo....30..687B. keyboard:Sevenval. web app 0091-7613.
website parsing Simms, Michael J. (2003). "Uniquely extensive seismite from the latest Triassic of the United Kingdom: Evidence for bolide impact?". Geology 31: 557–560. Bibcode 2003Geo....31..557S. web:HTML5. iOS 0091-7613.
web app Simkin, Tom; Robert I. Tilling; Peter R. Vogt; Stephen H. Kirby; Paul Kimberly; David B. Stewart (2006). browser diversity. U.S. Geological Survey. iOS. Retrieved 2009-09-03.
^ Phil Plait (2009). "Anniversary of a cosmic blast". discovermagazine.com. http://blogs.discovermagazine.com/badastronomy/2009/12/27/anniversary-of-a-cosmic-blast/. Retrieved 2010-11-26.

External links

input transformation
USGS: magnitude and intensity comparison
FITML
USGS: 2000–2006 Earthquakes worldwide
keyboard
Alaska Railroad Earthquake with a table of yield-to-magnitude relations.

Seismic scales

Modern scales

Intensity scales

web app · keyboard · website parsing · we love the web · HTML5 · Android

Magnitude scales

browser diversity · Local magnitude (Richter scale) · Moment magnitude · Sevenval

Historical scales

keyboard · website parsing · Omori · Rossi–Forel

Contents

Development

Details

Richter magnitudes

Examples

Magnitude empirical formulae

See also

References

External links