The red marker on the map is the epicenter of the earthquake, its origin was in the Pacific Ocean, on the eastern coast of Honshu Island, Japan, at a depth of 10 km, 87 km E-SE of Sendai, 297 km N-NE of Tokyo, the capital of Japan, and 337 km S-SE of Aumori.
|
Time in origin (GMT) |
Latitude, degree |
Longitude, degree |
Depth, km |
Stations number |
Ms/N |
mb/N |
I0 (calculated) |
GAP |
Center |
1
|
14:07:50.0
|
37.86 |
141.74 |
50.0 |
75
|
7.0/25 |
7.1/39 |
7.5 |
98
|
GS RAS(Verified) Federal research center, Geophysical survey of Russian Academy of Sciences
|
2
|
14:07:42.1
|
37.43 |
141.68 |
10.0 |
10
|
|
6.9/7 |
9.5-10 |
|
GS RAS(Preliminary) Federal research center, Geophysical survey of Russian Academy of Sciences
|
3
|
14:07:50.7
|
37.75 |
141.72 |
50.6 |
159
|
Mw 7.1/74 |
6.9/99 |
|
25
|
NEIC National Earthquakes Information Center of US Geological Service
|
4
|
14:07:52.1
|
37.43 |
141.65 |
60.0 |
315
|
Mw 7.1 |
|
|
33
|
CSEM European - Mediterranean seismological center
|
Fig. 1 presents fragments of records obtained from digital stations Matsushiro (∆ 3.1º), Erimo (∆ 4.3º), Yuzhno-Kurilsk (∆ 6.9º), Kurilsk (∆ 8.7º), Yuzhno-Sakhalinsk (∆ 9.1º). Fig. 2 presents fragments of records obtained from digital stations Kuldur (∆ 13.5º), Severo-Kurilsk (∆ 16.4º), Petropavlovsk (∆ 18.6º), Magadan (∆ 22.5º), Yakutsk (∆ 25.3º).
Image 1
Image 2
GS RAS registered seven aftershocks with М> = 4.6 within 20 hours after the main shock.
N |
Time in origin (GMT) |
Latitude, degree |
Longitude, degree |
Depth, km |
Stations number |
Ms/N |
mb/N |
I0 (calculated) |
Region |
20210643
|
13/02/2021 14:36:43.0.0 |
37.59 |
141.7 |
50.0 |
24 |
|
5.0/9 |
3 |
Near east coast of Honshu, Japan
|
20210644
|
13/02/2021 14:51:41.0.0 |
37.65 |
141.81 |
50.0 |
50 |
|
5.5/28 |
4-4.5 |
Near east coast of Honshu, Japan
|
20210647
|
13/02/2021 16:32:59.0.0 |
37.58 |
141.8 |
50.0 |
28 |
|
4.6/17 |
2 |
Near east coast of Honshu, Japan
|
20210652
|
14/02/2021 05:11:21.0.0 |
37.63 |
141.97 |
50.0 |
23 |
|
4.7/11 |
2-2.5 |
Near east coast of Honshu, Japan
|
20210653
|
14/02/2021 07:31:49.0.0 |
37.55 |
141.55 |
50.0 |
58 |
|
5.4/31 |
3.5-4 |
Near east coast of Honshu, Japan
|
20210654
|
14/02/2021 07:59:21.0.0 |
37.61 |
141.82 |
50.0 |
24 |
|
4.6/13 |
2 |
Near east coast of Honshu, Japan
|
20210658
|
14/02/2021 09:26:58.0.0 |
37.54 |
141.84 |
50.0 |
17 |
|
4.6/8 |
2 |
Near east coast of Honshu, Japan
|
The focal mechanism solution of the origin of this earthquake was calculated in GS RAS with signs of initial arrivals of P waves at 94 stations, including 70 stations which registered compression waves (plus signs) and 24 stations which registered tensile waves (minus signs). These stations are located in the interval of epicentral distances of 3.1-96.6º and in azimuth sector Az=3-353º. The focal mechanism solution in stereographic projection on the lower hemisphere and its elements are presented in the table. The table also contains focal mechanism solutions obtained at the USGS NEIC with W-phase Moment Tensor (Mww) technique and in Lamont-Dohert Earth Observatory of Columbia University, USA (LDEO GCMT) with СМТ (Centroid moment tensor) technique. Solutions from different centers are close. The earthquake occurred under the action of significant prevalence of compressive stresses oriented W-NW (AZ=288-298º). One nodal plane NP1 strikes S-SW (STK=192-204º) according to GS RAS and LDEO GCMT and S (STK=187º) according to USGS NEIC, another plane NP2 strikes N-NE (STK=28-34º). NP2 plan lies more flat (DP=32-43º) if compared with NP1 (DP=49-58º). The type of motion along both planes – reverse faults. Seismic moment of this earthquake was obtained in the GS RAS from P-wave spectrum registered at the station "Obninsk" (∆67.6º), it makes Mo=4.6*10**19 N*m, Mw=7.1. Seismic moment according to USGS NEIC makes Mo=4.831*10**19 N*m, Mww=7.1. According to LDEO GCMT it makes Mo=5.80*10**20 N*m, Mw=7.1.
Axes of main strengths |
Nodal planes |
Center |
|
T |
P |
N |
NP1 |
NP2 |
PI: 97
Azm: 76
|
PI: 13
Azm: 298
|
PI: 5
Azm: 207
|
Stk: 204
Dp: 58
Slip: 84
|
Stk: 34
Dp: 32
Slip: 99
|
GS RAS Federal research center, Geophysical survey of Russian Academy of Sciences
|
|
PI: 78
Azm: 33
|
PI: 3
Azm: 288
|
PI: 12
Azm: 197
|
Stk: 187
Dp: 49
Slip: 74
|
Stk: 30
Dp: 43
Slip: 107
|
NEIC National Earthquakes Information Center of US Geological Service
|
|
PI: 79
Azm: 63
|
PI: 8
Azm: 288
|
PI: 8
Azm: 197
|
Stk: 192
Dp: 53
Slip: 80
|
Stk: 28
Dp: 38
Slip: 103
|
GCMT Lamont-Doherty Earth Observatory Global CMT Columbia University, USA
|
|