Ohio-Penn EQ of Sept 25, 1998: Focal Mechanism & Moment Tensor

Harvard CMT Group

• The Harvard group has developed an extension of the large-EQ-technique that can be applied to smaller events
• The Harvard CMT moment tensor and "best" focal mechanism
• The moment magnitude (Mw) is just 4.5

MichSeis & OhioSeis

• A collaborative project to determine focal mechanism is underway.
  
• Preliminary Result #1 (Oct. 3): Initial look at P wave first motions at stations closer than 600 km:
  There is one significant violation of the Harvard CMT focal mechanism, a dilatational arrival in the middle of the compressional quadrant.
  Can not say too much until this violation can be confirmed.
  
• Click for plot of Harvard Focal Mechnaism with stations with P wave first motions
  (for R. Varga)