Early-est: Off East Coast of Honshu, Japan 2025.11.09-08:03:39.38 q:A mb:5.5 Mwp:6.9 Mwpd:- Td*T50Ex:5.2 fmamp_polarity: hash: fmamp_amp_aref: fmamp_amp_mwp:

Automatic solution - this event has not been reviewed by a seismologist
Automatically determined event information may be incorrect!

Earthquake Details:
Magnitude:	mb: 5.5 [231] Mwp: 6.9 [179] Mwpd: 7.0Xinv [166]
Region:	Off East Coast of Honshu, Japan
Origin Time:	2025.11.09-08:03:39.38 UTC
Hypocenter:	lat: 39.33° lon: 143.40° [+/-10km] depth: 10km [+/-8km]
Location Quality:	qualityCode: A stdErr: 1.3s assocPhases: 337 usedPhases: 275 minDist: 2.3° maxDist: 160.2° AzGap: 33° 2ndAzGap: 39° atten: -1.21 [+/-0.13]
Location Uncertainty:	68%ConfEllipse: minHorUnc: 6km maxHorUnc: 10km azMaxHorUnc: 119° 68%ConfEllipsoid: semiMajorAxisLength: 12km majorAxisAzimuth: 299° majorAxisPlunge: 5° semiIntermediateAxisLength: 8km intermediateAxisAzimuth: 201° intermediateAxisPlunge: 57° semiMinorAxisLength: 7km

Tsunamigeneic Assesment:

Discriminants:

Prob Underwater: >99%
T50Ex: 0.9 [220]    Td: 5.6s [27]    Td*T50Ex: 5.2 [27]    To: 68.5s [209]
Closest plate boundaries:
   Pacific \ Okhotsk [subduction zone]: distance: ~70km
   Okhotsk / Pacific [subduction zone]: distance: ~190km
Subduction geometry:    Zone: Kamchatka/Kurils/Japan    Slab depth at epicenter: 15km

Decision table (TEST!):

Event type:

Subduction Zone

Other Thrust/Normal

Strike-slip

Compatible close plate boundary?:

YES (70km)

Prob underwater:

>99%

Td*T50Ex:

5.2

Td*To:

383.6

Mwp magnitude:

6.9

Hypocenter depth:

10km

Slab depth at epicenter:

15km

First-motion Focal Mechanism (FMAMP_POLARITY):
Nodal Plane 1:	strike: 141° dip: 10° rake: 23°
Nodal Plane 2:	strike: 29° dip: 86° rake: 99°
Quality:	azimuthalGap: -1° stationPolarityCount: 271 misfitWeightCount: 35.9 misfit: 0.11 stationDistributionRatio: 0.64 meanDistP: 17.9 meanDistT: 15.5 qualityCode: B
Method:	methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_polarity

./hypo.1762675417430.mech.fmamp_polarity.mechanism.jpg

First-motion Focal Mechanism (HASH): (Warning: Unreliable solution, qualityCode=C)
Nodal Plane 1:	strike: 37° dip: 85° rake: 94°
Nodal Plane 2:	strike: 178° dip: 7° rake: 51°
Quality:	azimuthalGap: 33° stationPolarityCount: 271 misfit: 0.14 stationDistributionRatio: 0.62 rmsAngDiffAccPref: 32.73 fracAcc30degPref: 0.57 qualityCode: C
Method:	methodID: smi:gov.usgs/focalmec/HASH_1.2

./hypo.1762675417430.mech.hash.mechanism.jpg

First-motion Focal Mechanism (FMAMP_AMP_AREF): (Warning: Unreliable solution, qualityCode=C)
Nodal Plane 1:	strike: 136° dip: 24° rake: 30°
Nodal Plane 2:	strike: 18° dip: 78° rake: 111°
Quality:	azimuthalGap: -1° stationPolarityCount: 175 misfitWeightCount: 21.9 misfit: 9999.90 stationDistributionRatio: 0.48 meanDistP: 37.9 meanDistT: 24.5 qualityCode: C
Method:	methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_amp_aref

./hypo.1762675417430.mech.fmamp_amp_aref.mechanism.jpg

First-motion Focal Mechanism (FMAMP_AMP_MWP): (Warning: Unreliable solution, qualityCode=C)
Nodal Plane 1:	strike: 139° dip: 31° rake: 19°
Nodal Plane 2:	strike: 33° dip: 80° rake: 120°
Quality:	azimuthalGap: -1° stationPolarityCount: 150 misfitWeightCount: 19.0 misfit: 9999.90 stationDistributionRatio: 0.31 meanDistP: 34.2 meanDistT: 24.4 qualityCode: C
Method:	methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_amp_mwp

./hypo.1762675417430.mech.fmamp_amp_mwp.mechanism.jpg

Event ID: smi:KOERI/ee/event/1762675417430
Event info last updated: 2025.11.09-09:04:28 UTC
Event first association/location: 2025.11.09-08:07:47 UTC
Software: Early-est 1.2.0 (2016.06.27)
Agency: KOERI

Early-est: Off East Coast of Honshu, Japan 2025.11.09-08:03:39.38 q:A mb:5.5 Mwp:6.9 Mwpd:- Td*T50Ex:5.2 fmamp_polarity: hash: fmamp_amp_aref: fmamp_amp_mwp:

Automatic solution - this event has not been reviewed by a seismologist Automatically determined event information may be incorrect!

Automatic solution - this event has not been reviewed by a seismologist
Automatically determined event information may be incorrect!