Early-est:     Off East Coast of Honshu, Japan    2025.12.08-18:56:29.14    q:A      mb:5.5    Mwp:6.2    Mwpd:-    Td*T50Ex:1.7     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 [216]    Mwp: 6.2 [32]    Mwpd: 6.3Xinv [30] Region: Off East Coast of Honshu, Japan Origin Time: 2025.12.08-18:56:29.14 UTC Hypocenter: lat: 40.82°  lon: 143.17°  [+/-7km]    depth: 20km  [+/-7km] Location Quality: qualityCode:  A     stdErr: 1.4s   assocPhases: 301   usedPhases: 262 minDist: 1.2°   maxDist: 160.6°   AzGap: 59°   2ndAzGap: 68°   atten: -0.90 [+/-0.15] Location Uncertainty: 68%ConfEllipse:   minHorUnc: 5km   maxHorUnc: 7km   azMaxHorUnc: 129° 68%ConfEllipsoid:   semiMajorAxisLength: 8km   majorAxisAzimuth: 128°   majorAxisPlunge: 9°   semiIntermediateAxisLength: 7km   intermediateAxisAzimuth: 7°   intermediateAxisPlunge: 72°   semiMinorAxisLength: 7km Tsunamigeneic Assesment: Discriminants: Prob Underwater: >99% T50Ex: 0.5 [207]    Td: 3.5s [22]    Td*T50Ex: 1.7 [22]    To: 12.5s [186] Closest plate boundaries:    Pacific \ Okhotsk [subduction zone]: distance: ~110km    Okhotsk / Pacific [subduction zone]: distance: ~110km Subduction geometry:    Zone: Kamchatka/Kurils/Japan    Slab depth at epicenter: 27km Decision table (TEST!): Event type: Subduction Zone Other Thrust/Normal Strike-slip Compatible close plate boundary?:  YES (110km)  no  no Prob underwater:  >99%  >99%  >99% Td*T50Ex:    1.7    1.7    1.7 Td*To:      43.8      43.8      43.8 Mwp magnitude:        6.2        6.2        6.2 Hypocenter depth:        20km        20km        20km Slab depth at epicenter:        27km        -        -

First-motion Focal Mechanism (FMAMP_POLARITY):    (Warning: VERY UNRELIABLE SOLUTION, qualityCode=D) Nodal Plane 1: strike: 283°   dip: 57°   rake: 163° Nodal Plane 2: strike: 22°   dip: 76°   rake: 35° Quality: azimuthalGap: -1°   stationPolarityCount: 212   misfitWeightCount: 28.5   misfit: 0.28   stationDistributionRatio: 0.48   meanDistP: 42.4   meanDistT: 37.3   qualityCode: D Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_polarity
First-motion Focal Mechanism (HASH):    (Warning: VERY UNRELIABLE SOLUTION, qualityCode=D) Nodal Plane 1: strike: 198°   dip: 5°   rake: 97° Nodal Plane 2: strike: 11°   dip: 85°   rake: 89° Quality: azimuthalGap: 63°   stationPolarityCount: 212   misfit: 0.25   stationDistributionRatio: 0.64   rmsAngDiffAccPref: 37.14   fracAcc30degPref: 0.48   qualityCode: D 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: 49°   dip: 85°   rake: -4° Nodal Plane 2: strike: 139°   dip: 86°   rake: -175° Quality: azimuthalGap: -1°   stationPolarityCount: 99   misfitWeightCount: 15.5   misfit: 9999.90   stationDistributionRatio: 0.21   meanDistP: 31.6   meanDistT: 30.2   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: 112°   dip: 34°   rake: 18° Nodal Plane 2: strike: 7°   dip: 80°   rake: 122° Quality: azimuthalGap: -1°   stationPolarityCount: 26   misfitWeightCount: 5.2   misfit: 9999.90   stationDistributionRatio: 0.55   meanDistP: 40.1   meanDistT: 20.4   qualityCode: C Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_amp_mwp

Event ID: smi:KOERI/ee/event/1765220194381
Event info last updated: 2025.12.08-19:57:08 UTC
Event first association/location: 2025.12.08-18:58:45 UTC
Software: Early-est 1.2.0 (2016.06.27)
Agency: KOERI