THE POSSIBILITY OF INFERRING PALEOSEISMICITY FROM PALEOMAGNETIC DATING OF SPELEOTHEMS, WESTERN JAPAN

Paleomagnetic dating of continuously growing stalagmites by comparing their paleomagnetic records with a standard record, has been applied t o study the paleoseismic history of a region of western Japan. Three s talagmites (speleothems), which are assumed to have started growing si nce collapse of the limestone blocks on which they are formed, were co llected from two limestone caves located below the Akiyoshi plateau, w estern Japan. From the paleomagnetic results, it is estimated that the y began to grow at 6000, 2500 and 2000 yr B.P., respectively. On the a ssumption that their growth began immediately after their host limesto ne blocks fell, these three ages are interpreted to indicate the dates of past earthquakes in this region which triggered the break-off and fall of the blocks. Earthquakes are suggested because many huge collap sed limestone blocks and speleothems are observed in many caves in thi s region.