Early-est:     Off East Coast of Honshu, Japan    2026.03.26-14:18:53.42    q:A      mb:5.5    Mwp:6.6*    Mwpd:-    Td*T50Ex:5.3     fmamp_polarity:./hypo.1774534731533.mech.fmamp_polarity.thumb.jpg     fmamp_polarity_waveform:./hypo.1774534731533.mech.fmamp_polarity_waveform.thumb.jpg     hash:./hypo.1774534731533.mech.hash.thumb.jpg

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

Earthquake Details:
Magnitude: mb: 5.5 [118]    Mwp: 6.6* [75]    Mwpd: 6.7Xinv [75]
Region: Off East Coast of Honshu, Japan
Origin Time: 2026.03.26-14:18:53.42 UTC
Hypocenter: lat: 39.32°  lon: 143.33°  [+/-14km]    depth: 18km  [+/-13km]
Location Quality: qualityCode:  A     stdErr: 1.6s   assocPhases: 223   usedPhases: 135
minDist: 2.3°   maxDist: 158.4°   AzGap: 64°   2ndAzGap: 71°   atten: -0.97 [+/-0.13]
Location Uncertainty: 68%ConfEllipse:   minHorUnc: 11km   maxHorUnc: 14km   azMaxHorUnc: 170°
68%ConfEllipsoid:   semiMajorAxisLength: 17km   majorAxisAzimuth: 174°   majorAxisPlunge: 13°   semiIntermediateAxisLength: 15km   intermediateAxisAzimuth: 274°   intermediateAxisPlunge: 36°   semiMinorAxisLength: 12km
Tsunamigeneic Assesment:
Discriminants: Prob Underwater: >99%
T50Ex: 0.8 [120]    Td: 6.8s [17]    Td*T50Ex: 5.3 [17]    To: 64.9s [117]
Closest plate boundaries:
   Pacific \ Okhotsk [subduction zone]: distance: ~70km
   Okhotsk / Pacific [subduction zone]: distance: ~200km
Subduction geometry:    Zone: Kamchatka/Kurils/Japan: DEBUG: error: [Errno 2] No such file or directory: 'gmt'    Slab depth at epicenter: error: evaluating slab depth: -999.9
Decision table (TEST!):
Event type: Subduction Zone Other Thrust/Normal Strike-slip
Compatible close plate boundary?:
 YES (70km)
 no
 no
Prob underwater:
 >99%
 >99%
 >99%
Td*T50Ex:
   5.3
   5.3
   5.3
Td*To:
     441.3
     441.3
     441.3
Mwp magnitude:
       6.6*
       6.6*
       6.6*
Hypocenter depth:
       18km
       18km
       18km
Slab depth at epicenter:
       n/a
       -
       -
Tsunami and Rupture predictions (TEST!): No prediction: Event too small (Mwp<7.0) or too few Mwp readings (N<20)
./hypo.1774534731533.map.jpg

First-motion Focal Mechanism (FMAMP_POLARITY):
Nodal Plane 1: strike: 153°   dip: 12°   rake: 28°
Nodal Plane 2: strike: 35°   dip: 84°   rake: 101°
Quality: azimuthalGap: -1°   stationPolarityCount: 118   misfitWeightCount: 17.0   misfit: 0.09   stationDistributionRatio: 0.73   meanDistP: 31.1   meanDistT: 26.8   qualityCode: B
Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_polarity
./hypo.1774534731533.mech.fmamp_polarity.mechanism.jpg
First-motion Focal Mechanism (FMAMP_POLARITY_WAVEFORM):    (Warning: Unreliable solution, qualityCode=C)
Nodal Plane 1: strike: 121°   dip: 12°   rake: 19°
Nodal Plane 2: strike: 12°   dip: 86°   rake: 101°
Quality: azimuthalGap: -1°   stationPolarityCount: 31   misfitWeightCount: 5.5   misfit: 0.03   stationDistributionRatio: 0.59   meanDistP: 38.8   meanDistT: 36.0   qualityCode: C
Method: methodID: smi:net.alomax/focalmec/fmamp_0.0.5X_2016.06.14/_polarity_waveform
./hypo.1774534731533.mech.fmamp_polarity_waveform.mechanism.jpg
First-motion Focal Mechanism (HASH):    (Warning: Unreliable solution, qualityCode=C)
Nodal Plane 1: strike: 220°   dip: 19°   rake: 99°
Nodal Plane 2: strike: 30°   dip: 71°   rake: 87°
Quality: azimuthalGap: 98°   stationPolarityCount: 118   misfit: 0.23   stationDistributionRatio: 0.70   rmsAngDiffAccPref: 28.96   fracAcc30degPref: 0.74   qualityCode: C
Method: methodID: smi:gov.usgs/focalmec/HASH_1.2
./hypo.1774534731533.mech.hash.mechanism.jpg

Event ID: smi:alomax.net_BETA/author/ee/event/1774534731533
Event info last updated: 2026.03.26-15:17:02 UTC
Event first association/location: 2026.03.26-14:27:05 UTC
Software: Early-est 1.2.10 (2024.02.23)
Agency: alomax.net_BETA