They are Kikai-Akahoya (7.330 ka), Aira-Tanzawa (28.00 ka), Daisen-Kurayoshi (50.00 ka), Aso-4 (87.00 ka), Ata Torihama (250.0 ka), Kakuto (340.0 ka), Suiendani-TE5 (420.0 ka), Kobayashi-Sakura (540.0 ka), Kaisyo-Toriitoge (650.0 ka), Shishimuta-Azuki (870.0 ka), and Shishimuta-Pink (1000 ka).

The present earth surface and the Bruhnes/Matuyama paleomagnetic boundary (780.0 ka) play a same role as master tephra.

Ages of some master tephras are assigned rather arbitrarily, however, it is useful to affix them once to a specific value. A tephra sandwiched between two master tephras is afforded its age by interpolating the thicknesses of loess between them.

This technique, loess-chronometry, has the advantage of ability to measure an interval of tens to thousands years in geologic past, over radiometric dating.

More than 900 tephras are presently recorded and linked each other within a computer database including name, source volcano, age, magnitude, stratigraphy, and remarks.