Understanding Global Displacement Wavefields Graphs

Surface Waves

Travelling only through the crust, surface waves are of a lower frequency than body waves, and are easily distinguished on a seismogram as a result. Though they arrive after body waves, it is surface waves that are almost enitrely responsible for the damage and destruction associated with earthquakes. This damage and the strength of the surface waves are reduced in deeper earthquakes.

Love Waves

The first kind of surface wave is called a Love wave, named after A.E.H. Love, a British mathematician who worked out the mathematical model for this kind of wave in 1911. It’s the fastest surface wave and moves the ground from side-to-side. Confined to the surface of the crust, Love waves produce entirely horizontal motion

Rayleigh Waves

Rayleigh Waves Sketch
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The other kind of surface wave is the Rayleigh wave, named for John William Strutt, Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885. A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other waves

In the graphs below the Rayleigh waves can be seen as large M across the Time axis.

The graphs explained

Example 1.

On December 26, 2004 a M9.0 megathrust earthquake occurred off of the coast of Sumatra, Indonesia on the interface of the India and Burma plates. The event had unusually long rupture duration of ~ 600 seconds corresponding to slip on approximately 1200 kilometers of the subduction megathrust. The average displacement was roughly 15 meters [Lay et al., 2005]. The image below (Figure 1.) shows the global displacement wave field of the Mw 9.0 Sumatra-Andaman Islands earthquake as recorded by the radial component of the Global Seismographic Network (GSN). The R1 to R4 Rayleigh waves and their overtones are clearly evident with vertical ground motion of 1 cm or more. The closest station shown on the graph is CHTO located in Chiang Mai, Thailand at approximately 15.7 degrees near the epicenter.

GDW of the December 26, 2004 Sumatra-Andaman Islands Earthquake (Mw=9.0). The Rayleigh surface waves are indicated by R1-R4.

In the above graph, Stations marked by trace colour, name and distance in degrees from the epicenter. (top down)

trace colour, station name, degrees distance from epicenter
blue, PAYG: Puerto Ayora, Galapagos Islands, 173.24
black, TIEG: Tepich, Yucatan, Mexico, 156.01
red, HKT: Hockley, Texas, 144.79
red, EFI: Mount Kent, East Falkland Island, 127.08
light blue, PMSA: Palmer Station. Antarctica, 116.97
pink, COLA: College Outpost, Alaska, 97.67
blue, ALE: Alert, N.W.T., Canada, 93.55
red, TSUM: Tsumeb, Namibia, 80.14
blue, MAJO: Matsushiro, Japan, 51.06
red, TATO: Taipei, Taiwan, 32.73
blue, KMI: Kunming, Yunnan Province, China, 22.69
black, CHTO: Chiang Mai, Thailand, 15.69

Example 2.

In contrast with the Sumatran event, the Tohoku-Oki earthquake had a far more compact source and consisted of multiple events but the global displacement wavefield still shows significant energy in the R2 arrivals (Figure 2).

Global displacement wavefield of the March 11, 2011 Tohoku-Oki Earthquake (Mw=9.0). The Rayleigh surface waves are indicated by R1-R4

Stations List

Stations marked on the graphs vary event to event, often the same station will appear on multiple graphs, but this is not usual.

The full list of the 150 IRIS station abbreviations used in the graphs is shown below.
Station Code, Name, Latitude, Longitude, Elevation
AAK, Ala Archa, Kyrgyzstan, 42.639, 74.494, 1645
ABKT, Alibek, Turkmenistan, 37.93, 58.119, 678
ABPO, Ambohimpanompo, Madagascar, -19.018, 47.229, 1528
ADK, Adak, Aleutian Islands, Alaska, 51.882, -176.684, 130
AFI, Afiamalu, Samoa, -13.909, -171.777, 706
ALE, Alert, N.W.T., Canada, 82.503, -62.35, 60
ANMO, Albuquerque, New Mexico, USA, 34.946, -106.457, 1820
ANTO, Ankara, Turkey, 39.868, 32.793, 1090
ANWB, Willy Bob, Antigua and Barbuda, 17.669, -61.786, 39
ARU, Arti, Russia, 56.43, 58.562, 250
ASCN, Butt Crater, Ascension Island, -7.933, -14.36, 173
BBGH, Gun Hill, Barbados, 13.143, -59.559, 180
BBSR, Bermuda Institute of Ocean Sciences, St George’s Bermuda, 32.371, -64.696, 30
BCIP, Isla Barro Colorado, Panama, 9.166, -79.837, 61
BDFB, Brasilia, Brazil, -15.642, -48.015, 1195
BFO, Black Forest Observatory, Schiltach, Germany, 48.332, 8.331, 589
BGCA, Bogoin, Central African Republic, 5.176, 18.424, 676
BILL, Bilibino, Russia, 68.065, 166.453, 320
BJT, Baijiatuan, Beijing, China, 40.018, 116.168, 197
BORG, Borgarfjordur, Asbjarnarstadir, Iceland, 64.747, -21.327, 110
BOSA, Boshof, South Africa, -28.614, 25.256, 1280
BRVK, Borovoye, Kazakhstan, 53.058, 70.283, 330
CASY, Casey, Antarctica, -66.279, 110.535, 10
CCM, Cathedral Cave, Missouri, USA, 38.056, -91.245, 222
CHTO, Chiang Mai, Thailand, 18.814, 98.944, 420
CMLA, Cha de Macela, Sao Miguel Island, Azores, 37.764, -25.524, 429
COCO, West Island, Cocos (Keeling) Islands, -12.19, 96.835, 1
COLA, College Outpost, Alaska, USA, 64.874, -147.862, 200
COR, Corvallis, Oregon, USA, 44.586, -123.305, 110
CPUP, Villa Florida, Paraguay, -26.331, -57.331, 105
CTAO, Charters Towers, Australia, -20.088, 146.255, 357
DAV, Davao, Philippines, 7.07, 125.579, 150
DBIC, Dimbokro, Cote d’Ivoire, 6.67, -4.857, 125
DGAR, Diego Garcia, Chagos Islands, Indian Ocean, -7.412, 72.453, 1
DWPF, Disney Wilderness Preserve, Florida, USA, 28.11, -81.433, 30
EFI, Mount Kent, East Falkland Island, -51.675, -58.064, 110
ENH, Enshi, Hubei Province, China, 30.276, 109.494, 500
ERM, Erimo, Hokkaido Island, Japan, 42.015, 143.157, 40
ESK, Eskdalemuir, Scotland, UK, 55.317, -3.205, 242
FFC, Flin Flon, Canada, 54.725, -101.978, 338
FUNA, Funafuti, Tuvalu, -8.526, 179.197, 20
FURI, Mt. Furi, Ethiopia, 8.895, 38.68, 2570
GNI, Garni, Armenia, 40.148, 44.741, 1609
GRFO, Grafenberg, Germany, 49.691, 11.22, 384
GRGR, Grenville, Grenada, 12.132, -61.654, 195
GRTK, Grand Turk, Turks and Caicos Islands, 21.511, -71.133, 12
GTBY, Guantanamo Bay, Cuba, 19.927, -75.111, 79
GUMO, Guam, Mariana Islands, 13.589, 144.868, 170
HIA, Hailar, Neimenggu Autonomous Region, China, 49.27, 119.741, 620
HKT, Hockley, Texas, 29.962, -95.838, -413
HNR, Honiara, Solomon Islands, -9.439, 159.947, 100
HOPE, Hope Point, South Georgia Island, -54.284, -36.488, 20
HRV, Adam Dziewonski Observatory (Oak Ridge), Massachusetts, USA, 42.506, -71.558, 200
INCN, Inchon, Republic of Korea, 37.478, 126.624, 80
JOHN, Johnston Island, USA, 16.733, -169.529, 2
JTS, Las Juntas de Abangares, Costa Rica, 10.291, -84.953, 340
KAPI, Kappang, Sulawesi, Indonesia, -5.014, 119.752, 300
KBL, Kabul, Afghanistan, 34.541, 69.043, 1920
KBS, Ny-Alesund, Spitzbergen, Norway, 78.915, 11.938, 90
KDAK, Kodiak Island, Alaska, USA, 57.783, -152.583, 152
KEV, Kevo, Finland, 69.757, 27.003, 100
KIEV, Kiev, Ukraine, 50.701, 29.224, 180
KIP, Kipapa, Hawaii, USA, 21.42, -158.011, 110
KIV, Kislovodsk, Russia, 43.955, 42.686, 1054
KMBO, Kilima Mbogo, Kenya, -1.127, 37.252, 1950
KMI, Kunming, Yunnan Province, China, 25.123, 102.74, 1975
KNTN, Kanton, Kiritibati, -2.774, -171.719, 20
KONO, Kongsberg, Norway, 59.649, 9.598, 216
KOWA, Kowa, Mali, 14.497, -4.014, 321
KURK, Kurchatov, Kazakhstan, 50.715, 78.62, 184
KWAJ, Kwajalein Atoll, Pacific Ocean, 8.802, 167.613, 0
LBTB, Lobatse, Botswana, Africa, -25.015, 25.597, 1128
LCO, Las Campanas Astronomical Observatory, Chile, -29.011, -70.7, 2300
LPAZ, La Paz , Bolivia, -16.288, -68.131, 4817
LSA, Tibet, China, 29.703, 91.127, 3660
LSZ, Lusaka, Zambia, -15.278, 28.188, 1200
LVC, Limon Verde, Chile, -22.613, -68.911, 2960
LVZ, Lovozero, Russia, 67.898, 34.651, 630
MA2, Magadan, Russia, 59.576, 150.77, 339
MACI, Morro de la Arena, Canary Islands, 28.25, -16.508, 1674
MAJO, Matsushiro, Japan, 36.546, 138.204, 405
MAKZ, Makanchi, Kazakhstan, 46.808, 81.977, 600
MBAR, Mbarara, Uganda, -0.602, 30.738, 1390
MBWA, Marble Bar, Western Australia, -21.159, 119.731, 190
MDJ, Mudanjiang, Heilongjiang Province, China, 44.617, 129.591, 270
MIDW, Midway Island, USA, 28.216, -177.37, 20
MSEY, Mahe, Seychelles, -4.674, 55.479, 475
MSKU, Masuku, Gabon, -1.656, 13.612, 312
MSVF, Monasavu, Fiji, -17.745, 178.053, 801.1
MTDJ, Mount Denham, Jamaica, 18.226, -77.535, 925
NIL, Nilore, Pakistan, 33.651, 73.269, 629
NNA, Nana, Peru, -11.988, -76.842, 575
NRIL, Norilsk, Russia, 69.505, 88.441, 92
NWAO, Narrogin, Australia, -32.928, 117.239, 380
OBN, Obninsk, Russia, 55.115, 36.567, 160
OTAV, Otavalo, Ecuador, 0.238, -78.451, 3510
PAB, San Pablo, Spain, 39.545, -4.35, 950
PALK, Pallekele, Sri Lanka, 7.273, 80.702, 460
PAYG, Puerto Ayora, Galapagos Islands, -0.674, -90.286, 270
PET, Petropavlovsk, Russia, 53.023, 158.65, 110
PFO, Pinon Flat, California, USA, 33.611, -116.456, 1280
PLCA, Paso Flores, Argentina, -40.733, -70.551, 1050
PMG, Port Moresby, New Guinea, -9.405, 147.16, 90
PMSA, Palmer Station, Antarctica, -64.774, -64.049, 40
POHA, Pohakuloa, Hawaii, USA, 19.757, -155.533, 1990
PTCN, Pitcairn Island, South Pacific, -25.071, -130.095, 220
PTGA, Pitinga, Brazil, -0.731, -59.967, 237
QIZ, Qiongzhong, Hainan Province, China, 19.029, 109.844, 240
QSPA, South Pole Remote Earth Science Observatory (Quiet Zone), -89.929, 144.438, 2850
RAO, Raoul, Kermadec Islands, -29.245, -177.929, 60
RAR, Rarotonga, Cook Islands, -21.212, -159.773, 28
RAYN, Ar Rayn, Saudi Arabia, 23.523, 45.503, 631
RCBR, Riachuelo, Brazil, -5.827, -35.901, 400
RPN, Rapanui, Easter Island, Chile, -27.127, -109.334, 110
RSSD, Black Hills, South Dakota, USA, 44.121, -104.036, 2090
SACV, Santiago Island, Cape Verde, 14.97, -23.608, 387
SAML, Samuel, Brazil, -8.949, -63.183, 120
SBA, Scott Base, Antarctica, -77.849, 166.757, 50
SDDR, Presa de Sabenta, Dominican Republic, 18.982, -71.288, 589
SDV, Santo Domingo, Venezuela, 8.884, -70.634, 1620
SFJD, Sondre Stromfjord, Greenland, 66.996, -50.621, 330
SHEL, Horse Pasture, St. Helena Island, -15.959, -5.746, 537
SJG, San Juan, Puerto Rico, 18.109, -66.15, 420
SLBS, Sierra la Laguna Baja California Sur, Mexico, 23.686, -109.944, 825
SNZO, South Karori, New Zealand, -41.309, 174.704, 120
SSE, Shanghai, China, 31.095, 121.191, 40
SSPA, Standing Stone, Pennsylvania, 40.636, -77.888, 270
SUR, Sutherland, South Africa, -32.38, 20.812, 1770
TARA, Tarawa Island, Republic of Kiribati, 1.355, 172.923, 20
TATO, Taipei, Taiwan, 24.974, 121.497, 160
TAU, Hobart, Tasmania, Australia, -42.91, 147.32, 132
TEIG, Tepich, Yucatan, Mexico, 20.226, -88.276, 40
TGUH, Tegucigalpa, Honduras, 14.057, -87.273, 1151
TIXI, Tiksi, Russia, 71.634, 128.867, 40
TLY, Talaya, Russia, 51.681, 103.644, 579
TRIS, Tristan da Cunha, -37.068, -12.315, 60
TRQA, Tornquist, Argentina, -38.057, -61.979, 540
TSUM, Tsumeb, Namibia, -19.202, 17.584, 1260
TUC, Tucson, Arizona, 32.31, -110.785, 910
ULN, Ulaanbaatar, Mongolia, 47.865, 107.053, 1610
VNDA, Wright Valley (Bull Pass) Antarctica, -77.517, 161.853, 151
WAKE, Wake Island, 19.283, 166.652, 20
WCI, Wyandotte Cave, Indiana, USA, 38.229, -86.294, 210
WMQ, Urumqi, Xinjiang Province, China, 43.814, 87.705, 850
WRAB, Tennant Creek, NT, Australia, -19.934, 134.36, 366
WVT, Waverly, Tennessee, USA, 36.13, -87.83, 170
XAN, Xi’an, China, 34.031, 108.924, 630
XMAS, Kiritimati Island, Republic of Kiribati, 2.045, -157.446, 20
YAK, Yakutsk, Russia, 62.031, 129.68, 110
YSS, Yuzhno Sakhalinsk, Russia, 46.959, 142.76, 150

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