The red marker on the map is the epicenter of the earthquake, the origin was in the Pacific Ocean, on the east coast of Honshu Island, Japan, at a depth of 60 km, 79 km E-NE of Sendai, 264 km S-SE of Aumori and 360 km N-NE from Tokyo, capital of Japan.
|
Time in origin (GMT) |
Latitude, degree |
Longitude, degree |
Depth, km |
Stations number |
Ms/N |
mb/N |
I0 (calculated) |
GAP |
Center |
1
|
09:09:45.0
|
38.56 |
141.69 |
60.0 |
61
|
6.7/19 |
7.0/27 |
6.5-7 |
152
|
GS RAS(Verified) Federal research center, Geophysical survey of Russian Academy of Sciences
|
2
|
09:09:55.8
|
39.25 |
141.21 |
100.0 |
11
|
|
6.3/9 |
5-5.5 |
|
GS RAS(Preliminary) Federal research center, Geophysical survey of Russian Academy of Sciences
|
3
|
09:09:46.5
|
38.52 |
141.55 |
60.0 |
217
|
Mw 7.0 |
|
|
36
|
CSEM European - Mediterranean seismological center
|
4
|
09:09:45.3
|
38.48 |
141.67 |
54.0 |
110
|
Mw 7.0/26 |
|
|
60
|
NEIC National Earthquakes Information Center of US Geological Service
|
Fig. 1 presents fragments of records obtained from digital stations Matsushiro (∆ 3.4º), Yuzhno-Kurilsk (∆ 6.3º), Kurilsk (∆ 8.1º), Yuzhno-Sakhalinsk (∆ 8.4º), Vladivostok (∆ 8.7º),. Fig. 2 presents fragments of records obtained from digital stations Kuldur (∆ 12.9º), Severo-Kurilsk (∆ 15.8º), Petropavlovsk (∆ 18.3º), Magadan (∆ 21.8º), Yakutsk (∆ 24.6º).
Image 1
Image 2
GS RAS registered 2 aftershocks with М>=4.5 within the day after the main shock.
N |
Time in origin (GMT) |
Latitude, degree |
Longitude, degree |
Depth, km |
Stations number |
Ms/N |
mb/N |
I0 (calculated) |
Region |
20211339
|
20/03/2021 16:41:18.0.0 |
38.26 |
141.76 |
60.0 |
20 |
|
4.5/8 |
|
Near east coast of Honshu, Japan
|
20211344
|
20/03/2021 21:56:37.0.0 |
37.69 |
141.8 |
60.0 |
31 |
|
4.8/20 |
2-2.5 |
Near east coast of Honshu, Japan
|
The focal mechanism solution of the origin for the earthquake of March 3 was calculated in GS RAS with signs of initial arrivals of P waves at 65 stations, including 19 stations which registered compression waves (plus signs) and 46 stations which registered tensile waves (minus signs). These stations are located in the interval of epicentral distances of 2.4-95.6º and in azymuth sector Az=5-350º. 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 slight prevalence of compressive stresses oriented E-SE (AZ=107-114º). One nodal plane NP1 strikes to the south (STK=190-193º), another plane NP2 strikes N-NE (STK=21-28º). NP1 plane lies more flat (DP=20-24º) if compared with NP2 (DP=67-71º). The type of motion along NP1 – slip, along NP2 – reverse fault. The seismic moment according to USGS NEIC Mo=4.35*10**19 N*m, Mww=7. According to LDEO GCMT Mo=5.061*10**19 N*m, Mw=7.1.
Axes of main strengths |
Nodal planes |
Center |
|
T |
P |
N |
NP1 |
NP2 |
PI: 64
Azm: 306
|
PI: 26
Azm: 114
|
PI: 5
Azm: 207
|
Stk: 193
Dp: 20
Slip: 76
|
Stk: 28
Dp: 71
Slip: 95
|
GS RAS Federal research center, Geophysical survey of Russian Academy of Sciences
|
|
PI: 68
Azm: 298
|
PI: 22
Azm: 107
|
PI: 4
Azm: 199
|
Stk: 190
Dp: 24
Slip: 81
|
Stk: 21
Dp: 67
Slip: 94
|
NEIC National Earthquakes Information Center of US Geological Service
|
|
PI: 65
Azm: 298
|
PI: 24
Azm: 109
|
PI: 3
Azm: 200
|
Stk: 191
Dp: 21
Slip: 81
|
Stk: 22
Dp: 69
Slip: 94
|
GCMT Lamont-Doherty Earth Observatory Global CMT Columbia University, USA
|
|