Solar activity was quite low from January 2008 to February 2009, ever since the start of Solar Cycle 24. In 2008, the number of days in a year during which there were no sunspots was the fourth-largest since 1842. However, it is likely that the sunspot number would not have been able to reveal the solar inactivity in the beginning phase of cycle 24 because it hit the lower limit (zero) on more than two-thirds of the days of 2008. Geomagnetic data covers the longest span of time next to sunspot number, but its value has never reached that limit. The K-index, which is a geomagnetic index, from 2008 to the beginning of 2009, has been recorded at several observatories as being the smallest in the history of observation. The K p-index, which characterizes the geomagnetic planetary activity, has also significantly decreased. Taking into account the relation between the K p-index during the minimum phase of the solar cycle and sunspot numbers of the following maximum, it has been suggested that the peak solar activity in cycle 24 will be quite low. If solar activity in cycle 24 continues to be quiet, geomagnetic data are expected to be one of the key tools for monitoring space climate.

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Fig. 1. Hypocentral region of the 1964 Niigata earthquake and location of tidal stations used in the present analysis.

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The orientation error of in borehole array stations was obtained during the South Hyogo of Jan. 17, 1995. The four stations on reclaimed land and the other on stiff ground, were selected The displacement on the were carefully examined, and errors were detected The significance of the of orientation error was The stress-based 2D and/or 3D analyses were applied for one of the It was demonstrated that the method could reproduce the in the case that the base motion was used as the input motion.