EARTHQUAKE SUMMARY MAPU.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

1929

Wanganui

Nelson

Greymouth

Christchurch

Dunedin

Invercargill

Wellington

176°

176°

174°

174°

172°

172°

170°

170°

168°

168°

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42° 42°

44° 44°

46° 46°

N E W H E B RIDES TRE NC H

NOR TH NEW HEBR IDES T RENC H

TONG

A TR

ENCH

KERM

ADEC

TRE

NCH

S O U T H P A C I F I C O C E A N

T A S M A N S E A

C O R A L S E ANew

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NewCaled on ia(F r anc e )

Kerm ad

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Cam pb e l l I s . ( N . Z. )

A uck la nd Is . (N . Z .)

A nt ipo de I . (N .Z .)

Macq ua rie Is lan d(A us .)

Cha tha m Is lan d

Tong

a Isl a

nds

S o c ie ty I sl a nd s

Kerm

adec

Isla

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Ta sma n F r a c t u r e Z o n e

A l p i n e F a u l t

A U S T R A L I A

N E W Z E A L A N D

V A N U A T U

S o u t hTa s m a n

R i s e

Ea s tTa sm a nPla te a u

C a m p b e l lP l a t e a u

C h a t h a m

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N o r t hF i j i

B a s i n

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Tas m

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Ta s m a n B a s i n

L o u i s v i l e R i d g e

SO U T HIS L AN D

N O RT HIS L AN D

TASM A NI A (A us. )

P A C I F I CP L A T E

NEWHEBRIDES

PLATE

KERMADECPLATE

BALMORALREEFPLATE

CONWAYREEFPLATE

NIUAFO'OUPLATE

TONGAPLATE

60 mm/yr

115 mm/yr

35-45 mm/yrAUSTRALIAN PLATE

PACIFIC PLATE

PUYS

EGUR

TREN

CH

Brisbane

Sydney

AucklandMelbourne

160°

160°

170°

170°

180°

180°

170°

170°

160°

160°

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150°

30° 30°

40° 40°

50° 50°

M6.3 South Island, New Zealand Earthquake of 21 February 2011

0 200 400100Kilometers

Mercator Projection

A U S T R A L I ANew Caledonia

VANUATU

NEW ZEALAND

Brisbane

Sydney

AucklandMelbourne

160°

160°

170°

170°

180°

180°

170°

170°

160°

160°

150°

150°

30° 30°

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0 400 800 1,200 1,600200Kilometers

Prepared in cooperation with the Global Seismographic Network

Tectonic Setting

Seismic Hazard

Epicentral Region

Tectonic Summary

The February 21, 2011 South Island, New Zealand earthquake occurred as part ofthe aftershock sequence of the M 7.0 September 3, 2010 Darfield, NZearthquake. The February 21 earthquake involved oblique-reverse faulting at theeasternmost limit of previous aftershocks, and like the mainshock itself is broadlyassociated with regional plate boundary deformation as the Pacific and Australiaplates interact in the central South Island, New Zealand.

This latest shock is significantly closer to the main population center ofChristchurch, NZ, than is the September 2010 mainshock, in the vicinity ofseveral other moderate (M 4 - 5) sized aftershocks located east of the mainrupture zone of the 2010 event. There is no specific structure directly linking thisevent to the main fault of the 2010 mainshock, although there have beennumerous aftershocks along generally east-west linear trends extending east fromthe end of the previous rupture. The north or north-east trends to the possiblefault planes and the oblique thrust faulting mechanism as seen in the focalmechanism solution may reflect an association with similarly- trending faultspreviously mapped in the Port Hills region, just to the south of Christchurch.

Since the September 3, 2010 mainshock, there have been approximately 6M>=5.0 aftershocks in the Christchurch region. The February 21 earthquakerepresents the largest aftershock to date, more that half a magnitude unit largerthan the previous largest aftershock.

EXPLANATIONEarthquake Magnitude

5.50 - 5.996.00 - 6.997.00 - 7.99≥ 8.00

Earthquake Depth0 - 6970 - 299≥ 300

After Sept. 3rd, 2010 Main Shock MAG

1.5 - 2.52.5 - 3.03.0 - 4.04.0 - 5.1Greendale Fault

Seismic hazard is expressed as peakground acceleration (PGA) on firmrock, in meters/sec², expected to beexceeded in a 50-yr period with aprobability of 10 percent.

EXPLANATIONMag ≥ 7.0

0 - 69 km70 - 299300 - 600

Plate BoundarySubductionTransformDivergentOthers

Volcanoes

RELATIVE PLATE MOTIONS

The broad red vectors represent the motion of tectonic platesrelative to the adjacent plate. In the vicinity of this earthquake,the Australia Plate and Pacific Plate are converging at about 35-45 mm/yr.

0 400 800 1,200 1,600200Kilometers

Significant Earthquakes Mag >= 6.5

Year Mon Day Time Lat Long Dep Mag1901 11 15 2015 -43.000 173.000 0 6.81929 03 09 1050 -43.227 173.002 15.2 6.91929 06 16 2247 -41.831 172.292 35 7.51938 12 16 1721 -45.503 166.880 25 6.91942 06 24 1116 -41.534 175.630 35 7.01942 08 01 1234 -41.066 175.684 35 6.91943 08 02 0046 -45.000 167.000 0 6.81960 05 24 1446 -43.962 167.824 35 6.71961 12 27 2348 -41.243 175.754 35 6.81968 05 23 1724 -41.743 172.123 46.7 7.21976 05 04 1356 -44.726 167.663 30.4 6.61988 06 03 2327 -45.039 167.587 74.8 6.71989 05 31 0554 -45.302 167.071 23.2 6.51993 08 10 0051 -45.207 166.958 28 7.01994 06 18 0325 -43.081 171.610 14 6.72003 08 21 1212 -45.104 167.144 28 7.22007 10 15 1229 -44.796 167.553 18 6.82009 07 15 0922 -45.762 166.562 12 7.82010 09 03 1635 -43.530 171.812 12 7.0

Peak Ground Acceleration in m/sec**2

.2 .4 .8 1.6 2.4 3.2 4.0 4.8

Epicentral Region

Epicentral Region

DISCLAIMER

Base map data, such as place names and political boundaries, are the best available but may not be current or may contain inaccuracies and therefore should not be regraded as having official signifiance.

Map prepared by U.S. Geological Survey National Earthquake Information Center21 February 2011http://earthquake.usgs.gov/Map not approved for release by Director USGS

PLATE TECTONICSBird, P., 2003, An updated digital model of plate boundaries: Geochem. Geophys. Geosyst., v. 4, no. 3, pp. 1027- 80.

BASE MAP NIMA and ESRI, Digital Chart of the World USGS, EROS Data Center NOAA GEBCO and GLOBE Elevation Models

PAGER

ShakeMap

Christchurch

173.5° E173° E172.5° E172° E171.5° E171° E

43° S

43.5° S

44° S

M6.3 South Island, New Zealand Earthquake of 21 February 2011 21 February 2011 23:51:43 UTC 43.6° S., 172.71° E.Depth 5 kmMw = 6.1 (USGS)

DATA SOURCES and REFERENCES

EARTHQUAKES AND SEISMIC HAZARD USGS, National Earthquake Information Center NOAA, National Geophysical Data Center IASPEI, Centennial Catalog (1900 - 1999) and extensions Engdahl, E.R. and Villaseñor, A., 2002, Global Seismicity: 1900 - 1999, chap. 41 of Lee, W.H.K., and others,eds., International Earthquake and Engineering Seismology, Part A: New York, N.Y., Elsevier Academeic Press, 932 p.HDF (unpublished earthquake catalog) (Engdahl, 2003)Global Seismic Hazard Assessment Program http://www.seismo.ethz.ch/GSHAP/GNS Science New Zealand (Earthquakes since 09/03 mainshock)EOS, transactions, American Geophysical Union,Vol.91 #49, p469-470 (Greendale Fault Trace)NASA (SRTM 3-arc second imagery for inset),http://gcmd.nasa.gov/records/GCMD_DMA_DTED.html