💾 Archived View for federal.cx › earthquake.gmi captured on 2024-05-26 at 14:50:05. Gemini links have been rewritten to link to archived content
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Earthquake Magnitude Scale Magnitude Earthquake Effects Number/year(est.) 2.5 or less Usually not felt, but can be recorded by seismograph. 900,000 2.5 to 5.4 Often felt, but only causes minor damage. 30,000 5.5 to 6.0 Slight damage to buildings and other structures. 500 6.1 to 6.9 May cause a lot of damage in very populated areas. 100 7.0 to 7.9 Major earthquake. Serious damage. 20 8.0 or greater Great earthquake. Total destruction near epicenter. One every 5 to 10 years Earthquake Magnitude Classes Earthquakes are also classified in categories ranging from minor to great. Class Magnitude Great 8 or more Major 7 - 7.9 Strong 6 - 6.9 Moderate 5 - 5.9 Light 4 - 4.9 Minor 3 - 3.9
(GMT, m > 1.7, 60sec)
05/26 18:05:59 1.84ml 5 km SW of Volcano, Hawaii (19.4112 -155.2710)
05/26 18:05:11 2.87ml 8 km SSW of Pāhala, Hawaii (19.1307 -155.4955)
05/26 17:54:51 4.30mb 100 km E of Murghob, Tajikistan (38.2854 75.1023)
05/26 17:52:14 1.91md 9 km ENE of Pāhala, Hawaii (19.2498 -155.4020)
05/26 17:51:34 1.80ml 54 km W of Tatitlek, Alaska (60.9075 -147.6737)
05/26 17:31:03 4.50mb 72 km NE of Masohi, Indonesia (-2.7818 129.3732)
05/26 17:18:59 2.00ml 3 km WNW of Lindsay, Texas (31.3880 -103.5720)
05/26 17:16:31 2.10ml 11 km WNW of Tilden, Texas (28.5100 -98.6510)
05/26 17:02:59 1.94md 11 km ENE of Pāhala, Hawaii (19.2500 -155.3797)
05/26 16:57:37 2.20ml 42 km ENE of Susitna North, Alaska (62.3577 -149.1462)
05/26 16:30:18 2.05md 13 km ENE of Pāhala, Hawaii (19.2685 -155.3678)
05/26 16:27:07 1.98ml 14 km S of Fern Forest, Hawaii (19.3380 -155.1173)
05/26 16:23:25 4.10mb 58 km NW of Bandar-e Lengeh, Iran (26.9641 54.4990)
05/26 15:29:41 1.80ml 56 km S of Cantwell, Alaska (62.8986 -149.1657)
05/26 15:15:12 4.50mb 4 km W of Antimácheia, Greece (36.8039 27.0503)
05/26 15:04:21 2.10ml 27 km WSW of Denali Park, Alaska (63.6186 -149.3977)
05/26 14:25:26 1.90md 19 km SE of Pāhala, Hawaii (19.0555 -155.3725)
05/26 14:24:09 5.20mb 122 km ESE of Antofagasta, Chile (-24.1754 -69.3366)
05/26 13:56:09 2.32md 5 km NW of The Geysers, CA (38.7943 -122.8075)
05/26 13:42:22 4.70mb 109 km S of Vanimo, Papua New Guinea (-3.6766 141.2781)
05/26 13:26:23 4.30mb 281 km E of Levuka, Fiji (-17.8622 -178.0352)
05/26 12:59:09 2.56md 66 km W of Ferndale, CA (40.5227 -125.0403)
05/26 12:51:46 1.90ml 66 km NNE of Van Horn, Texas (31.5870 -104.5540)
05/26 12:23:41 1.75md 4 km SW of Volcano, Hawaii (19.4158 -155.2623)
05/26 11:58:26 4.40mb 132 km E of Barcelona, Philippines (8.3105 127.6293)
05/26 11:54:03 2.45ml 13 km WNW of Puako, Hawaii (20.0073 -155.9573)
05/26 11:53:51 2.36ml 13 km ENE of Pāhala, Hawaii (19.2552 -155.3667)
05/26 11:32:04 1.96ml 10 km ENE of Pāhala, Hawaii (19.2388 -155.3887)
05/26 11:21:12 2.31md 5 km WSW of Central Aguirre, Puerto Rico (17.9298 -66.2708)
05/26 10:43:10 1.84md 9 km ENE of Pāhala, Hawaii (19.2460 -155.4048)
05/26 10:23:26 2.83md 3 km SE of Indios, Puerto Rico (17.9665 -66.7972)
05/26 10:19:46 3.30ml off the coast of Oregon (43.8376 -129.2881)
05/26 09:53:19 2.10ml 3 km NNW of Houston, Alaska (61.6537 -149.8505)
05/26 09:35:38 2.60ml 130 km WSW of Port Orford, Oregon (42.3823 -126.0085)
05/26 09:04:39 1.79ml 13 km S of Fern Forest, Hawaii (19.3408 -155.1417)
05/26 08:51:01 3.13md 77 km NW of San Antonio, Puerto Rico (19.0473 -67.5415)
05/26 08:43:11 2.64md 2 km SE of Indios, Puerto Rico (17.9770 -66.7992)
05/26 08:41:31 2.63md 8 km NW of Rincón, Puerto Rico (18.3942 -67.3118)
05/26 08:29:02 2.32md 2 km SW of Pāhala, Hawaii (19.1867 -155.4992)
05/26 08:09:15 2.27md 42 km NNE of Covelo, CA (40.1475 -123.0928)
05/26 07:01:52 4.30mb Mariana Islands region (21.5744 142.9844)
05/26 06:39:38 1.92ml 8 km NW of Prague, Oklahoma (35.5518 -96.7417)
05/26 06:33:10 3.00ml 68 km SW of Nanwalek, Alaska (58.8864 -152.6864)
05/26 06:21:47 1.84md 8 km WNW of Cobb, CA (38.8415 -122.8078)
05/26 06:20:53 2.59md 7 km WNW of Cobb, CA (38.8347 -122.8057)
05/26 06:17:05 5.10mb Pacific-Antarctic Ridge (-54.7179 -130.4780)
05/26 05:41:34 3.20ml 114 km SSW of Lanai City, Hawaii (19.8996 -157.4175)
05/26 05:27:11 2.58md 3 km WNW of Orocovis, Puerto Rico (18.2412 -66.4195)
05/26 05:05:36 4.50mb south of the Fiji Islands (-22.0671 -179.5636)
05/26 04:37:10 4.60mb 15 km WNW of Progreso, Panama (8.4812 -82.9749)
05/26 04:32:01 2.08md 4 km N of Midway, Arkansas (36.4302 -92.4593)
05/26 04:13:39 4.60mb 80 km WSW of San Juan, Peru (-15.7607 -75.7869)
05/26 03:59:18 4.70mb 19 km E of Lapuan, Philippines (6.1509 125.8798)
05/26 03:45:41 2.47md 0 km SE of Indios, Puerto Rico (17.9877 -66.8135)
05/26 03:37:09 2.20ml 110 km SE of Yakutat, Alaska (59.0019 -138.1137)
05/26 03:06:24 1.75ml 7 km SSE of Volcano, Hawaii (19.3740 -155.2140)
05/26 02:52:19 1.91ml 7 km WSW of Radersburg, Montana (46.1713 -111.7288)
05/26 02:46:04 2.30ml 47 km ENE of Pedro Bay, Alaska (59.9541 -153.3331)
05/26 02:45:56 2.00ml 19 km NNW of Karluk, Alaska (57.7295 -154.5802)
05/26 02:43:36 2.09md 1 km SE of Indios, Puerto Rico (17.9845 -66.8093)
05/26 02:41:53 1.80ml 12 km NNW of Sutcliffe, Nevada (40.0484 -119.6630)
05/26 02:32:34 2.03md 10 km ENE of Pāhala, Hawaii (19.2463 -155.3928)
05/26 02:17:09 2.34md 8 km of Petrolia, CA (40.3933 -124.3080)
05/26 01:20:25 2.00ml 37 km E of Pedro Bay, Alaska (59.8288 -153.4391)
05/26 01:14:09 1.80ml 7 km E of Lowell Point, Alaska (60.0618 -149.3024)
05/26 00:29:59 2.10ml 39 km N of Petersville, Alaska (62.8488 -150.7937)
05/26 00:13:17 2.33md 2 km SE of Indios, Puerto Rico (17.9805 -66.8035)
05/26 00:01:14 2.50ml 54 km NW of Toyah, Texas (31.6620 -104.1980)
05/25 23:31:16 4.40mb 262 km E of Levuka, Fiji (-18.0734 -178.2051)
05/25 23:31:16 1.87md 5 km NNE of Pāhala, Hawaii (19.2500 -155.4595)
05/25 23:18:05 3.25md 60 km N of Isabela, Puerto Rico (19.0440 -67.1133)
05/25 23:06:38 1.80ml 62 km ENE of Pedro Bay, Alaska (60.0072 -153.0695)
05/25 23:03:00 2.30ml 12 km ESE of Pāhala, Hawaii (19.1460 -155.3732)
05/25 22:56:02 2.00ml 5 km NNE of Big Lake, Alaska (61.5670 -149.9147)
05/25 22:23:16 6.30mww 83 km NNW of Port-Vila, Vanuatu (-17.1088 167.8842)
05/25 22:11:53 1.90ml 19 km W of Karluk, Alaska (57.5440 -154.7737)
05/25 21:44:27 1.90ml 7 km SSE of Central, Alaska (65.5084 -144.7345)
05/25 21:24:03 4.40mb 76 km NNE of Calama, Chile (-21.8780 -68.5266)
05/25 21:13:50 2.46ml 19 km WSW of Volcano, Hawaii (19.4023 -155.4185)
05/25 21:01:25 1.90ml 31 km WSW of Nanwalek, Alaska (59.2973 -152.4570)
05/25 20:11:39 1.90ml 7 km N of Tilden, Texas (28.5270 -98.5600)
05/25 20:11:37 4.80mww 11 km WSW of Canoas, Costa Rica (8.4925 -82.9318)
05/25 19:39:38 1.91ml 19 km N of Pine Mountain Club, CA (35.0138 -119.1775)
05/25 19:08:26 1.91md 23 km SE of Naalehu, Hawaii (18.9342 -155.4122)
05/25 18:59:01 4.90mb 149 km NNW of Pototano, Indonesia (-7.0985 117.1803)
The magnitude reported is that which the U.S. Geological Survey considers official for this earthquake, and was the best available estimate of the earthquake's size, at the time that this page was created. Other magnitudes associated with web pages linked from here are those determined at various times following the earthquake with different types of seismic data. Although they are legitimate estimates of magnitude, the U.S. Geological Survey does not consider them to be the preferred "official" magnitude for the event.
Earthquake magnitude is a measure of the size of an earthquake at its source. It is a logarithmic measure. At the same distance from the earthquake, the amplitude of the seismic waves from which the magnitude is determined are approximately 10 times as large during a magnitude 5 earthquake as during a magnitude 4 earthquake. The total amount of energy released by the earthquake usually goes up by a larger factor: for many commonly used magnitude types, the total energy of an average earthquake goes up by a factor of approximately 32 for each unit increase in magnitude.
There are various ways that magnitude may be calculated from seismograms. Different methods are effective for different sizes of earthquakes and different distances between the earthquake source and the recording station. The various magnitude types are generally defined so as to yield magnitude values that agree to within a few-tenths of a magnitude-unit for earthquakes in a middle range of recorded-earthquake sizes, but the various magnitude-types may have values that differ by more than a magnitude-unit for very large and very small earthquakes as well as for some specific classes of seismic source. This is because earthquakes are commonly complex events that release energy over a wide range of frequencies and at varying amounts as the faulting or rupture process occurs. The various types of magnitude measure different aspects of the seismic radiation (e.g., low-frequency energy vs. high-frequency energy). The relationship among values of different magnitude types that are assigned to a particular seismic event may enable the seismologist to better understand the processes at the focus of the seismic event. The various magnitude-types are not all available at the same time for a particular earthquake.
Preliminary magnitudes based on incomplete but rapidly-available data are sometimes estimated and reported. For example, the Tsunami Warning Centers will calculate a preliminary magnitude and location for an event as soon as sufficient data are available to make an estimate. In this case, time is of the essence in order to broadcast a warning if tsunami waves are likely to be generated by the event. Such preliminary magnitudes are superseded by improved estimates of magnitude as more data become available.
For large earthquakes of the present era, the magnitude that is ultimately selected as the preferred magnitude for reporting to the public is commonly a moment magnitude that is based on the scalar seismic-moment of an earthquake determined by calculation of the seismic moment-tensor that best accounts for the character of the seismic waves generated by the earthquake. The scalar seismic-moment, a parameter of the seismic moment-tensor, can also be estimated via the multiplicative product rigidity of faulted rock x area of fault rupture x average fault displacement during the earthquake.
Magnitude Type, Magnitude Range, Distance Range, Equation
Mww (Moment W-phase)(generic notation Mw) ~5.0 and larger 1 - 90 degrees MW = 2/3 * (log10(MO) - 16.1),where MO is the seismic moment.
Note this is also unit-dependent; the formula above is for moment in dyne-cm. If using metric units (N.m), the constant is 9.1. Derived from a centroid moment tensor inversion of the W-phase (~50-2000 s; pass band based on size of EQ). Computed for all M5.0 or larger earthquakes worldwide, but generally robust for all M5.5 worldwide. Provides consistent results to M~4.5 within a regional network of high-quality broadband stations. Authoritative USGS magnitude if computed.
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Mwc (centroid) ~5.5 and larger 20 - 180 degrees MW = 2/3 * (log10(MO) - 16.1), where MO is the seismic moment.
Derived from a centroid moment tensor inversion of the long-period surface waves (~100-2000 s; pass band based on size of EQ). Generally computable for all M6.0 worldwide using primarily the Global Seismograph Network. Only authoritative if Mww is not computed, not published otherwise.
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Mwb (body wave) ~5.5 to ~7.0 30 - 90 degrees MW = 2/3 * (log10(MO) - 16.1), where MO is the seismic moment.
Derived from moment tensor inversion of long-period (~20-200 s; pass band based on size of EQ) body-waves (P- and SH). Generally computable for all M5.5 or larger events worldwide. Source complexity at larger magnitudes (~M7.5 or greater) generally limits applicability. Only authoritative if Mww and Mwc are not computed.
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Mwr (regional) ~4.0 to ~6.5 0 - 10 degrees MW = 2/3 * (log10(MO) - 16.1), where MO is the seismic moment.
Based on the scalar seismic-moment of the earthquake, derived from moment tensor inversion of the whole seismogram at regional distances (~10-100 s; pass band based on size of EQ). Source complexity and dimensions at larger magnitudes (~M7.0 or greater) generally limits applicability. Authoritative for <M5.0. Within the continental US and south-central Alaska where we have a large number of high quality broadband stations we expect we can compute an Mwr consistently for events as small as M4.0. In some areas of the country, with relatively dense broadband coverage, we can compute Mwr consistently to as small as M3.5.
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Ms20 or Ms (20sec surface wave) ~5.0 to ~8.5 20 - 160 degrees MS = log10 (A/T) 1.66 log10 (D) 3.30 .i
A magnitude based on the amplitude of Rayleigh surface waves measured at a period near 20 sec. Waveforms are shaped to the WWSSN LP response. Reported by NEIC, but rarely used as authoritative, since at these magnitudes there is almost always an Mw available. Ms is primarily valuable for large (>6), shallow events, providing secondary confirmation on their size. Ms_20 tends to saturate at about M8.3 or larger.
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mb (short-period body wave) ~4.0 to ~6.5 15 - 100 degrees mb = log10(A/T) Q(D,h) ,where A is the amplitude of ground motion (in microns); T is the corresponding period (in seconds); and Q(D,h) is a correction factor that is a function of distance, D(degrees), between epicenter and station and focal depth, h (in kilometers), of the earthquake.
Based on the amplitude of 1st arriving P-waves at periods of about 1 s. Waveforms are shaped to the WWSSN SP response. Reported for most M4.0-4.5 to 6.5 EQs that are observed teleseismically. Only authoritative for global seismicity for which there is no Mww, Mwc, Mwb or Mwr, typically 4.0-5.5 range. Mb tends to saturate at about M 6.5 or larger.
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Mfa (felt-area magnitude) any any various
An estimate of body-wave (mb) magnitude based on the size of the area over which the earthquake was felt, typically assigned to widely felt earthquakes that occurred before the invention of seismographs and to earthquakes occurring in the early decades of seismograph deployment for which magnitudes calculated from seismographic data are not available. The computations are based on isoseismal maps or defined felt areas using various intensity-magnitude or felt area-magnitude formulas. Reference: Seismicity of the United States, 1568-1989 (Revised), by Carl W. Stover and Jerry L. Coffman, U.S. Geological Survey Professional Paper 1527, United States Government Printing Office, Washington: 1993.
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ML Ml, or ml (local) ~2.0 to ~6.5 0 - 600 km
The original magnitude relationship defined by Richter and Gutenberg in 1935 for local earthquakes. It is based on the maximum amplitude of a seismogram recorded on a Wood-Anderson torsion seismograph. Although these instruments are no longer widely in use, ML values are calculated using modern instrumentation with appropriate adjustments. Reported by NEIC for all earthquakes in the US and Canada. Only authoritative for smaller events, typically M<4.0 for which there is no mb or moment magnitude. In the central and eastern United States, NEIC also computes ML, but restricts the distance range to 0-150 km. In that area it is only authoritative if there is no mb_Lg as well as no mb or moment magnitude.
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mb_Lg, mb_lg, or MLg (short-period surface wave) ~3.5 to ~7.0 150-1110 km (10 degres)
A magnitude for regional earthquakes based on the amplitude of the Lg surface waves as recorded on short-period instruments. Only authoritative for smaller events in the central and eastern United States, typically <4.0 for which there is no mb or moment magnitude.
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Md or md (duration) ~4 or smaller 0 - 400 km
Based on the duration of shaking as measured by the time decay of the amplitude of the seismogram. Sometimes the only magnitude available for very small events, but often used (especially in the past) to compute magnitude from seismograms with "clipped" waveforms due to limited dynamic recording range of analog instrumentation, which makes it impossible to measure peak amplitudes. Computed by NEIC but only published when there is no other magnitude available.
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Mi or Mwp (integrated p-wave) ~5.0 to ~8.0 all
Based on an estimate of moment calculated from the integral of the displacement of the P wave recorded on broadband instruments.
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Me (energy) ~3.5 and larger all Me = 2/3 log10E - 2.9,where E is the energy calculated by log10E = 11.8 1.5MS where energy, E, is expressed in ergs.
Based on the seismic energy radiated by the earthquake as estimated by integration of digital waveforms.
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Mh any any N/A
Non-standard magnitude method. Generally used when standard methods will not work. Sometimes use as a temporary designation until the magnitude is finalized.
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Finite Fault Modeling ~7.0 and larger 30 - 90 degrees
FFM modeling provides a kinematic description of faulting including estimates of maximum slip, area of rupture and moment release as a function of time. Results are used to provide constraints on fault dimensions and slip used in damage assessment modeling (ShakeMap, PAGER) and to model stress changes (Coulomb stress modeling) on the active fault and/or adjacent faults.
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Mint (intensity magnitude) any any various
A magnitude estimated from the maximum reported intensity, typically for earthquakes occurring before seismic instruments were in general use. This has been used for events where the felt reports were from too few places to use a magnitude determined from a felt area. Reference: Catalog of Hawaiian earthquakes, 1823-1959, by Fred W. Klein and Thomas L. Wright U.S. Geological Survey Professional Paper 1623, USGS Information Services, Denver: 2000.
