Space conditions during a month of a sequence of six M > 6.8 earthquakes ending with the tsunami of 26 December 2004

Abstract. This paper examines space and seismological data for the time period about one month before the giant Sumatra-Andaman strong (9.3) earthquake (EQ). The combination of seismological and space data reveals some interesting features for this time period: (1) six successive high speed solar wind streams obviously triggering a sudden increase of geomagnetic activity were all followed by strong to giant (M > 6.8) EQs, (2) the 6 strong EQs present certain spatial-temporal constraints, with the epicentre of the EQs occuring at the edges of the Pacific Plate (the Sumatra-Andaman EQ occurred at the end of this series of EQs, eastward of the first one), in a clockwise direction, (3) the EQs occurred after a sudden increase of geomagnetic activity, as inferred from the 3 h-K_p index, following a quiet geomagnetic period and (4) the time delay of the M > 6.2 earthquakes (in the broad area examined) from the last maximum sudden K_p increase was on average ~1.5 days. These findings from the study of the Earth's space environment during the month preceding the Sumatra-Andaman giant (9.3) EQ provide new information for a possible better understanding of the Sun-magnetosphere-lithosphere coupling.