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Information message about a strong earthquake near Hokkaido, Japan, April 24, 2018.

A strong earthquake with M = 6 occurred on April 24, 2018 at 08:53 GMT (11:53 Moscow time) near the island of Hokkaido, Japan.

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 10 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).

Preliminary processing has been done with data from 33 stations, accurate processing - with data from 75.

The red marker on the map shows the epicenter of the earthquake, whose focus was near the island of Hokkaido, Japan, at a depth of 90 km, 27 km E-SE of Nemuro, Japan, 86 km south of Yuzhno-Kurilsk, Russia and in 270 km SW of Kurilsk, Russia.

	Time in origin (GMT)	Latitude, degree	Longitude, degree	Depth, km	Stations number	Ms/N	mb/N	I0 (calculated)	GAP	Center
1	08:53:18.1	43.25	145.91	90.0	75		6.0/38	5	87	GS RAS(Verified) Federal research center, Geophysical survey of Russian Academy of Sciences
2	08:53:22.9	43.43	145.74	100.0	33		6.1/15	4.5-5		GS RAS(Preliminary) Federal research center, Geophysical survey of Russian Academy of Sciences
3	08:53:21.0	43.32	145.74	80.0	644	Mw 5.5	5.5		49	CSEM European - Mediterranean seismological center
4	08:53:21.7	43.36	145.74	80.0	124	Mw 5.5	5.5		49	NEIC National Earthquakes Information Center of US Geological Service
5	08:53:00.0	43.3	145.8	90.0		5.3				JMA Japan Meteorological Agency

Fig. 1 presents fragments of records obtained from digital stations Yuzhno-Kurilsk (∆ 0.8º), Erimo (∆ 2.4º), Kurilsk (∆ 2.4º), Yuzhno-Sakhalinsk (∆ 4.3º), Matsushiro (∆ 8.9º). Fig. 2 presents fragments of records obtained from digital stations Ussuriysk (∆ 10.1º), Kuldur (∆ 11.5º), Magadan (∆ 16.6º), Yakutsk (∆ 21.1º), Ulaanbaatar (∆ 27.4º).

Image 1

Image 2

According to FIC EGS RAS the earthquake was felt in Yuzhno-Kurilsk with intensity of 4-5 MSK, in Malokurilsky, Goryachy beach with intensity of 4 MSK. Fig. 1 presents the intensity map which was obtained from the Japanese Meteorological Agency JMA.

Image 1

Click here to view detailed macroseismic data (DyfitWeb service)

The focal mechanism solution in stereographic projection on the lower hemisphere and its elements are presented in the table below. It was obtained in USGS NEIC with W-phase Moment Tensor (Mww) technique and in Lamont-Dohert Earth Observatory, Columbia University, USA (LDEO GCMT) with СМТ (Centroid moment tensor) technique. Solutions based on data from different centers are close. The earthquake occurred under the prevaling action of tensile stresses oriented to N-N-W. One nodal plane NP1 strikes NE (STK=48-63º) and is flat (DP=20-26º), another nodal plane NP2 strikes W-S-W (STK=248-258º) and is steeply dipping (DP=65-71º). the type of motion along NP1 – flat fault with right latteral slip components, for NP2 – fault with left latteral slip components. According to USGS NEIC – Mo=2.16*10**17 N*m, Mw=5.5, according to LDEO GCMT – Mo=2.91*10**17 N*m, Mw=5.6.

Axes of main strengths			Nodal planes		Center
T	P	N	NP1	NP2	Center
PI: 20 Azm: 343	PI: 70 Azm: 181	PI: 6 Azm: 75	Stk: 63 Dp: 26 Slip: -103	Stk: 258 Dp: 65 Slip: -84	NEIC National Earthquakes Information Center of US Geological Service
PI: 26 Azm: 333	PI: 63 Azm: 168	PI: 6 Azm: 66	Stk: 48 Dp: 20 Slip: -109	Stk: 248 Dp: 71 Slip: -83	GCMT Lamont-Doherty Earth Observatory Global CMT Columbia University, USA