Seismicity of Russia and the Former Soviet UnionIntroduction | Source Catalogs | Regional Catalogs | Seismic Stations | Documentation | Bibliography
Altai Seismicity Map and Composite Regional CatalogEXCEL
Altai, a "Russification" of Turkish word Alatau or Alatoo, means "mottled mountain" (whitish-blue snow on top, gray rocks, golden and dark green forests with numerous bright-red tulips( they really are mottled. There are many coal mines and quarries in the region, which are important for producing iron for factories in the Ural Mountain region. Seismic events from blasting activities make up about half of the events recorded here.
The first earthquake documented here was in the year 1716, and the 31 catalog events that are known from before 1900 were characterized by macroseismic data. Of the 80 earthquakes documented between 1900 and 1961, only 7 were listed in the Obninsk Bulletin (1955-61). Until 1921, the origin times are quite imprecise, with errors ranging from hours to years. Later, from 1927 till 1960, errors in to became less, ranging from 3-5 sec. to 20 sec.
Local seismic stations began operating in 1962. Some of the earthquakes that are included in the Obninsk Catalog are therefore not present in the ESSN catalog.
After 1961, the estimates of error that were included in the General Catalog were excluded from the Altai Regional Catalog. Only beginning about 1980 did origin time errors became as small as 1-2 sec., while from 1962 through the 1970s they range from 1-2 sec. to 10 sec.
The local surveys contributing to the ESSN usually did not estimate the depth at all, reasonably believing that errors are too serious to say more than that all of the events are inside the upper part of the crust.
The depth values in the General Catalog are mostly just assumed (e.g., 3, 15 or 33 km). The value of 15 km was assumed as "typical". Values of 3 or 33 were taken from the Obninsk Bulletin, and mean no more than to indicate the kind Travel Time Table used in the determination. Depth values different from these three are probably based on the seismological recordings when nearest station was close to epicenter.
The Altai region has numerous quarries with active blasting. The Local seismological survey generally tried to identify these events as distinct from natural earthquakes and exclude then from the Catalogs. The time distribution of events 1962-1990, after this "cleaning," appears as follows:
Local time is usually GMT +7 hours. Note that the maximum seismic activity is from 05-07h GMT (i.e., 12:00-14:00 local time, corresponding roughly to the lunch break). The second peak of activity falls at 09-13 GMT (16:00-20:00 local time, the end of workday), a typical time to prepare the quarry for the next day. So, regardless of efforts by local seismologists to get information about blasting, we estimate that many tens of blast events escaped the "filtering" process, were linked into ESSN, and therefore are included in the Altai Composite Regional catalog.