Information message about the strong earthquake at the South Island of New Zealand, February 21, 2011. |
| The strong earthquake with M=6.3 occurred at the South Island of New Zealand on February 21, 2011 at 23:51 GMT (February 22, 2011 at 02:51 Moscow time). It caused victims and destructions. |
| Parameters of the earthquake
have been determined in the Alert Service (AS) of Information
Processing Center (IPC) of Geophysical Survey of RAS in Obninsk with station data
obtained from digital and analog seismic stations of Russia, countries of CIS
and from abroad. Alert message on this earthquake has been delivered in 28 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 24 stations, accurate processing - with data 33 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Tennant Creek (∆ 39.7º), Port Moresby (∆ 40.7º), Sanae (∆ 64.9º), Erimo (∆ 89.3º), Taejon (∆ 89.7º). Fig. 2 presents fragments of records obtained from digital stations Tiksi (∆ 119.1º), Kurchatov (∆ 124.3º), Borovoe (∆ 130º), Arti (∆ 137.4º), Garni (∆ 141.5º). |
Figure 1
| 
Figure 2
|
|
| IPC GS RAS also has obtained information with parameters of this event from some seismological centers, these data are given in table 1: |
| Table 1 |
| NN |
Time in origin h-min-s (GMT) |
Lat degr. |
Lon degr. |
Depth km |
N s/st |
Ms/ N |
mb/ N |
I0 calc |
GAP |
Center | | 1 |
23-51-41.9 |
-43.68 |
172.56 |
10 |
33 |
6.3/19 | 6.3/10 | 8.5-9 | 92 | IPC GS RAS (Accurate) | | 2 |
23-51-41.7 |
-43.73 |
172.57 |
10 |
24 |
| 6.3/9 | 8.5 | 92 | IPC GS RAS (Preliminary) | | 3 |
23-51-45.2 |
-43.57 |
173 |
33 |
216 |
| 6.1 | | 52 | CSEM | | 4 |
23-51-43.0 |
-43.6 |
172.71 |
5 |
|
6.3/41 | 6.1/73 | | | NEIC | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| CSEM - European - Mediterranean seismological center |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Epicenter |
| Fig.3 presents with red star epicenter of this earthquake, it's origin was located at the South Island of New Zealand, at the depth of 10 km, 20 km S-S-W from Christchurch town and 320 km S-W from Wellington. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 2 aftershocks with М>=5.7 within two hours after the main shock. |
| N |
Date & Time (GMT)
yy-mm-dd hh:mm:sec |
Lat
degr. |
Lon
degr. |
Depth
km |
N
station |
Ms/ N |
mb/ N |
Io
calc. |
Region |
| 20110660 | 2011-02-22 00:04:18.0 | -43.69 | 172.55 | 10 | 18 | - | 5.8/ 4 | 7-7.5 | South Island, New Zealand | | 20110661 | 2011-02-22 01:50:30.0 | -43.65 | 172.49 | 20 | 19 | - | 5.7/ 6 | 6 | South Island, New Zealand | |
| Macroseismic manifestations |
| In accordance with RIA-Novosti , underground shocks became the reason of significant destructions in Christchurch town. From the latest news 147 people were killed and the destiny of 50 persons is unknown. This destructive earthquake almost fully destroyed central part of the town. Numerous buildings were significantly damaged, includinf central cathedral, a few districts became useless for living.
Economical damage from this earthquake is estimated as 15 millions of dollars. Prime minister John Kay called this earthquake as "the most dramatic event".
Fig. 4, downloaded from WEB site of NEIC USA, presents the map with intensities obtained from phone calls from 121 respondents in 35 local sites.
|
Figure 4 |
|
| Historical records |
| Epicenter of this earthquake was located in 68 km East from destructive earthquake which occurred at the South Island of New Zealand on September 3, 2010. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions for the origin of this earthquake which occurred on February 21, 2011 at 23:51 GMT were obtained with CMT method in NEIC USA, USGS and Global CMT Catalog, USA. All solutions are almost identical.
This earthquake occurred under prevailing action of compression forces oriented N-W–S-E. Axis of expansion force was N-E oriented. One nodal plane (NP1) has nearly along meridional direction of propagation, another plane (NP2) – N-E direction of propagation. Both nodal planes are rather steeply falling (DP=56-64º), the type of motion along both planes – shifts with uplift components (along NP1 plane – left side slip, along NP2 plane – right side slip). Focal mechanism in stereographic projection at lower hemisphere is presented in figures 5, 6, elements of this mechanism are presented in table 2.
The value of seismic moment Мо of this earthquake which occurred on February 21, 2011 in accordance with USGS makes 1.9*10**18 n*m, the value of moment magnitude makes Mw=6.1; and in accordance with Global CMT – Мо=1.92*10**18 n*m, Mw=6.1.
|
| Table 2 |
| Axes of main strengths |
Nodal planes |
Center |
| T |
P |
N |
NP1 |
NP2 |
| Pl |
Azm |
Pl |
Azm |
Pl |
Azm |
Stk |
Dp |
Slip |
Stk |
Dp |
Slip |
| 45 | 28 | 5 | 293 |
44 | 198 | 170 | 64 | 39 | 60 |
56 | 148 | NEIC | | 44 | 20 | 4 | 114 |
46 | 208 | 167 | 57 | 32 | 59 |
64 | 143 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 5 | 
Figure 6 |
|
