U.S. DEPARTMENT OF THE INTERIOR EARTHQUAKE SUMMARY MAP U.S. GEOLOGICAL SURVEY

Prepared in cooperation with the M8.0 Samoa Islands Region Earthquake of 29 September 2009 Global Seismographic Network

M

a

r s Epicentral Region h

a M A R S H A L L l I S TL A eN DcS tonic Setting l 174° 176° 178° 180° 178° 176° 174° 172° 170° 168° 166° C e n t r a l 160° 170° I 180° 170° 160° 150° s l a P a c i f i c K M e l a n e s i a n n L NORTH a d B a s i n i p B a s i n s n Chris tmas Island i H e BISMARCK n C g I

R N s PLATE a l B R I TA i G E I s E W N T R 0° m a 0° N E R N e i n P A C I F I C 10° 10° C a H l T d b r s

a e r C P L A T E n t E g I D n e i s A Z o l M e a t u r SOUTH n R r a c d E K I R I B A T I s F s K g o BISMARCK l a p a PLATE P A C I F I C G a Solomon Islands P L A T E

S O L O M O N T U V A L U V I T Y I S L A N D S A Z TR FUTUNA PLATE 12° 12° S EN O U C BALMORAL C 10° T H H o 10° S O REEF o WOODLARK L Santa k O M Cruz PLATE I PLATE O N T RE N C H Sam sl Is lands oa I NIUAFO'OU a N s n C o r a l S e a S A M O A lan d SOLOMON SEA O d PLATE T s s U B a s i n R A M E R I C A N (N A PLATE T M H . S A M O A Z O . N N o r t h ( U . S . ) ) T E F I J I U W New F i j i I S L A N D S S A Hebrides o H c R E B a s i n i C 14° 14° C O R A L S E A B et Tahiti H R y V A N U A T U EXPLANATI PION I NEW I D s sl F R E N C H P O L Y N E S I A E d a E H L HEBRIDES n nd ( F R A N C E ) S C s A H a l G C N 20° T PLATE s 20° O N I E Mag ≥ 7.0 R E E R a R N T g T A' n New C S o E A H T 0 - 69 km 1981 Caledonia I D G R N (France) E B H O N E W T TONGA A A N u u 70 - 299 CONWAY PLATE s 1917 S o u t h s t o REEF t r ra r a l F i j i l 16° 16° f PLATE I F s 300 - 600 1975 o s la B a s i n d r a n l n d a c Brisbane k s l t s u I r

R Plate Be oundary c e Z L d i o a n

d o e m

g r r N e

30° d e e K 30° w Transform H H C o C a KERMADEC N w . l E Divergent s A e I R e PLATE 1962 d c T

e 18° 18° o R d C S O U T H PA C I F I CO thOersC E A N 1994 a 1909 n E m i i D a r H s e A K C e B M n a Volcanoes R N i s Epicentral Region i n E E a K l Auckland R P T 1950 NORTH L S n TA S M A N S E A ISLAND o E Samoa Islands a u i ID m s 1919 s v R i 1962 1913 a N E W Z E A L A N D B 1903 29 September 2009 6:17:48 UTC 40° l e 40° T 20° E 20° R H 1919 i 2006 A l p i n e F a u l t d 15.509° S., 172.034° W. g W s e E Depth 18 km Ta s m a n B a s i n N 1937 d n 1948 Mw = 8 (USGS) 160° 170° 180° 170° 160° 150° East Chatham Island a H H C Tasman C h a t h a m R i s e l C N E Plateau R s T At least 110 people killed in Samoa, 22 people in American Kilometers N RELATIVE PLATE MOTIONS I A SOUTH E G 0 200 400 800 1,200 1,600 N Samoa and seven people on Niuatoputapu, Tonga. O ISLAND R T 35-45 mm/yr 1990 a Widespread damage to infrastructure at Pago Pago, T The broad red vector representsH the motion of the 22° g American Samoa, in many parts of Samoa and on 22° C 1997 A with respect to the Australia plNate in the epicentral region. n E Niuatoputapu, Tonga. Felt (V) at Apia, Samoa and (IV) at R o G T N Tafuna, American Samoa. Felt in much of American Samoa, R PACIFIC PLATE T U O Samoa and northern Tonga. A tsunami with wave heights G 1977 E T S EXPLANATION (peak-to-trough) was recorded at: 314 cm at Pago Pago, Distance (km) Y 2009 A A' U American Samoa; 140 cm at Apia, Samoa; 47 cm at P -900 -800 -700 -600 -500 -400 -300 -200 -100 0 100 Seismic Hazard Earthquake Magnitude Rarotonga and 8 cm at Penrhyn, Cook Islands; 14 cm at 1980 Nuku`alofa, Tonga; 11 cm at Papeete, French . 150° 160° 170° 180° 170° 160° 150° 0 0 5.50 - 5.99 24° 1982 24°

6.00 - 6.99 -100 -100

0° 0° 7.00 - 7.99 1963 -200 -200

1932 ) ≥ 8.00 s m New Ireland d New k -300 -300 INDONESIA (

Britain SOLOMON 2007 Earthquake Dep2t6h° n 26°

PAPUA h

ChoisIeSuLl ANDS t NEW GUINEA Bougainville a p P.N.G. Santa Isabel 0 - 69 l -400 -400 e s Malaita D 10° 10° 70 - 299 I Guadalcanal -500 -500 San Cristobal 1905 ≥ 300 c e H -600 -600 C d 1986 28° N 28° a E 1955 VANUATU R m 1959 T -900 -800 -700 -600 -500 -400 -300 -200 -100 0 100

r C 1917 E 20° 20° e D A U S T R A L I A 174° 176° 178° 180° K 178° 176A° 174° 172° 170° 168° 166° New Caledonia M Kilometers R E 0 100 200 400 K

Brisbane

30° 30° DISCUSSION

The broad-scale tectonics of the Tonga region are dominated by the relative DATA SOURCES and REFERENCES Sydney convergence of the Pacific and Australia plates, with the Pacific plate subducting Significant Earthquakes Mag >= 7.5 Epicentral Region westward beneath the Australia plate at the . At the latitude of the EARTHQUAKES AND SEISMIC HAZARD earthquake of September 29, 2009, the Pacific plate moves westward with respect Year Mon Day Time Lat Long Dep Mag USGS, National Earthquake Information Center Auckland to the interior of the Australia plate at a velocity of about 86 mm/year. The 1903 01 04 0507 -20.000 -175.000 400 8.0 NOAA, National Geophysical Data Center 1913 06 26 0457 -20.000 -174.000 0 7.7 IASPEI, Centennial Catalog (1900 - 1999) and earthquake occurred near the northern end of a 3,000 km long segment of the extensions Engdahl, E.R. and Villaseñor, A., Pacific/Australia plate boundary that trends north-northeast.; farther north of the 1917 06 26 0549 -15.500 -173.000 0 8.5 1919 01 01 0300 -19.971 -177.914 202 7.7 2002, Global Seismicity: 1900 - 1999, chap. 41 earthquakes source region, the plate boundary trends northwest and then west. of Lee, W.H.K., and others,eds., International 40° 40° The eastern edge of the broad Australia plate may be viewed as a collection of 1919 04 30 0717 -19.823 -172.215 35 8.2 Earthquake and Engineering Seismology, small plates or microplates that move with respect to each other and with respect 1937 04 16 0301 -20.768 -177.144 348 7.5 Part A: New York, N.Y., Elsevier Academeic 1948 09 08 1509 -21.000 -174.000 0 8.0 Press, 932 p. to the Pacific plate and the Australia plate interior. 1950 12 14 0152 -19.250 -175.750 200 7.5 EHB catalog (Engdahl et al., 1998) 1957 04 14 1918 -15.403 -173.129 35 7.5 HDF (unpublished earthquake catalog) (Engdahl, 2003) 150° 160° 170° 180° 170° 160° 150° On the basis of currently available location and mechanism information, we Global Seismic Hazard Assessment Program 1962 05 21 2115 -19.962 -177.272 416 7.5 http://www.seismo.ethz.ch/GSHAP/ Kilometers infer that the September 29 earthquake occurred as a normal fault rupture on or Seismic hazard is expressed as peak 1975 12 26 1556 -16.241 -172.364 15 7.7 0 200 400 800 1,200 1,600 near the outer rise of the subducting Pacific plate. ground acceleration (PGA) on firm 1981 09 01 0929 -15.112 -173.019 14.2 7.5 Bird, P., 2003, An updated digital model of plate DISCLAIMER rock, in meters/sec², expected to be 2006 05 03 1526 -20.187 -174.123 55 8.0 boundaries: Geochem. Geophys. Geosyst., v. 4, The broad-scale Australia/Pacific plate boundary is one of the most active no. 3, pp. 1027- 80. Base map data, such as place names and political exceeded in a 50-yr period with a Peak Ground Acceleration in m/sec**2 2009 09 29 0648 -15.560 -172.070 18 8.0 earthquake regions in the world. Earthquakes occur on the thrust-fault boundary BASE MAP boundaries, are the best available but may not be probability of 10 percent. current or may contain inaccuracies and therefore between the Australia and Pacific plates, within the Pacific plate on both sides of NIMA and ESRI, Digital Chart of the World USGS, EROS Data Center should not be regraded as having official signifiance. the trench, and within and on the boundaries of the small plates that compose the NOAA GEBCO and GLOBE Elevation Models Map prepared by U.S. Geological Survey National .2 .4 .8 1.6 2.4 3.2 4.0 4.8 eastern edge of the overall Australia plate. Earthquake Information Center 2 October 2009 http://earthquake.usgs.gov/ Map not approved for release by Director USGS