Early-est:     Off East Coast of Honshu, Japan    2025.12.08-21:52:41.32    q:A      mb:5.5    Mwp:6.8    Mwpd:-    Td*T50Ex:4.4     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 [224]    Mwp: 6.8 [178]    Mwpd: 6.9Xinv [172] Region: Off East Coast of Honshu, Japan Origin Time: 2025.12.08-21:52:41.32 UTC Hypocenter: lat: 40.84°  lon: 143.25°  [+/-7km]    depth: 10km  [+/-7km] Location Quality: qualityCode:  A     stdErr: 1.6s   assocPhases: 363   usedPhases: 288 minDist: 1.2°   maxDist: 161.0°   AzGap: 31°   2ndAzGap: 45°   atten: -1.09 [+/-0.14] Location Uncertainty: 68%ConfEllipse:   minHorUnc: 5km   maxHorUnc: 7km   azMaxHorUnc: 124° 68%ConfEllipsoid:   semiMajorAxisLength: 8km   majorAxisAzimuth: 302°   majorAxisPlunge: 8°   semiIntermediateAxisLength: 7km   intermediateAxisAzimuth: 190°   intermediateAxisPlunge: 70°   semiMinorAxisLength: 6km Tsunamigeneic Assesment: Discriminants: Prob Underwater: >99% T50Ex: 0.8 [224]    Td: 5.8s [35]    Td*T50Ex: 4.4 [35]    To: 54.7s [213] Closest plate boundaries:    Pacific \ Okhotsk [subduction zone]: distance: ~100km    Okhotsk / Pacific [subduction zone]: distance: ~100km Subduction geometry:    Zone: Kamchatka/Kurils/Japan    Slab depth at epicenter: 26km Decision table (TEST!): Event type: Subduction Zone Other Thrust/Normal Strike-slip Compatible close plate boundary?:  YES (100km)  no  no Prob underwater:  >99%  >99%  >99% Td*T50Ex:    4.4    4.4    4.4 Td*To:      317.3      317.3      317.3 Mwp magnitude:        6.8        6.8        6.8 Hypocenter depth:        10km        10km        10km Slab depth at epicenter:        26km        -        -

First-motion Focal Mechanism (FMAMP_POLARITY): Nodal Plane 1: strike: 137°   dip: 13°   rake: 28° Nodal Plane 2: strike: 20°   dip: 84°   rake: 102° Quality: azimuthalGap: -1°   stationPolarityCount: 278   misfitWeightCount: 37.0   misfit: 0.14   stationDistributionRatio: 0.64   meanDistP: 15.9   meanDistT: 13.9   qualityCode: B Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_polarity
First-motion Focal Mechanism (HASH):    (Warning: Unreliable solution, qualityCode=C) Nodal Plane 1: strike: 9°   dip: 75°   rake: 91° Nodal Plane 2: strike: 185°   dip: 15°   rake: 86° Quality: azimuthalGap: 31°   stationPolarityCount: 278   misfit: 0.19   stationDistributionRatio: 0.61   rmsAngDiffAccPref: 35.81   fracAcc30degPref: 0.52   qualityCode: C Method: methodID: smi:gov.usgs/focalmec/HASH_1.2
First-motion Focal Mechanism (FMAMP_AMP_AREF):    (Warning: Unreliable solution, qualityCode=C) Nodal Plane 1: strike: 129°   dip: 5°   rake: 40° Nodal Plane 2: strike: 359°   dip: 87°   rake: 94° Quality: azimuthalGap: -1°   stationPolarityCount: 181   misfitWeightCount: 24.1   misfit: 9999.90   stationDistributionRatio: 0.31   meanDistP: 41.1   meanDistT: 25.1   qualityCode: C Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_amp_aref
First-motion Focal Mechanism (FMAMP_AMP_MWP):    (Warning: Unreliable solution, qualityCode=C) Nodal Plane 1: strike: 263°   dip: 20°   rake: 152° Nodal Plane 2: strike: 20°   dip: 81°   rake: 72° Quality: azimuthalGap: -1°   stationPolarityCount: 156   misfitWeightCount: 21.8   misfit: 9999.90   stationDistributionRatio: 0.28   meanDistP: 34.3   meanDistT: 28.7   qualityCode: C Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_amp_mwp

Event ID: smi:KOERI/ee/event/1765230761723
Event info last updated: 2025.12.08-22:53:23 UTC
Event first association/location: 2025.12.08-21:56:50 UTC
Software: Early-est 1.2.0 (2016.06.27)
Agency: KOERI