State-of-the-art of historical earthquake research in Fennoscandia and the Baltic Republics

We review historical earthquake research in Northern Europe. 'Historical' is defined as being identical with seismic events occurring in the pre-instrumental and early instrumental periods between 1073 and the mid-1960s. The first seismographs in this region were installed in Uppsala, Sweden and Bergen, Norway in 1904-1905, but these mechanical pendulum instruments were broad band and amplification factors were modest at around 500. Until the 1960s few modern short period electromagnetic seismographs were deployed. Scientific earthquake studies in this region began during the first decades of the 1800s, while the systematic use of macroseismic questionnaires commenced at the end of that century. Basic research efforts have vigorously been pursued from the 1970s onwards because of the mandatory seismic risk studies for commissioning nuclear power plants in Sweden, Finland, NW Russia, Kola and installations of huge oil platforms in the North Sea. The most comprehensive earthquake database currently available for Northern Europe is the FENCAT catalogue covering about six centuries and representing the accumulation of work conducted by many scientists during the last 200 years. This catalogue is given in parametric form, while original macroseismic observations and intensity maps for the largest earthquakes can be found in various national publications, often in local languages. No database giving intensity data points exists in computerized form for the region. The FENCAT catalogue still contains some spurious events of various kinds but more serious are some recent claims that some of the presumed largest historical earthquakes have been assigned too large magnitude values, which would have implications for earthquake hazard levels implemented in national building codes. We discuss future cooperative measures such as establishing macroseismic data archives as a means for promoting further research on historical earthquakes in Northern Europe

20. Nihon no Kansoku-ten de miidasareta P-ha no Soji no Ijyo (Dai ippo)

The P-wave travel times to Japanese stations were investigated. Kurile Islands earthquakes gave arrivals earlier than those expected from the Jeffreys-Bullen table. Neither location errors nor reading errors are likely to be the cause of this phenomenon. The early arrivals may be due to a high velocity structure beneath the Island Arc from the Kuriles to Japan. It is found that the upper boundary of this high-velocity structure is dipping toward south west and not shallower than 60km. Its thickness is increasing in the same direction and the lower boundary is not deeper than 400km. This pronounced anomalous structure could not be found in any direction other than that of the Kurile Islands. The seismic waves which travel in this anomalous region are less attenuated than those travelling elsewhere, especially in higher frequency range.|Nihon no kansoku ten made no P-ha no soji o shirabeta. Chishima no jishin wa Jeffreys-Bullen hyo kara kitaisareru yorimo hayai totatsu-jikoku o ataeru. Shino kettei aruiwa yomitori no gosa ga kono gensyo no gen\u27in towa kangaerarezu, Chishima kara Nihon made no kojyo-retto no shita no kosokudo kozo ni yoru mono to omowareru. Kono kosokudo kozo no jyogen wa nan-seini shitamuki ni katamuiteori, 60km yori mo asaku wa naranai. Kono kozo no atsusa wa onajiku nansei-hoko ni zokashi, sono kagen wa 400 km yori mo fukaku wa nai. Kono ijyo-kozo wa Chishima-retto igai no dono hoko kara mo miidasarenai. Kono ijyo-chiiki o toru jishin no nami wa tokuni koshuha-ryoiki ni oite hokano basho kara kita nami to kurabete gensui ga sukunai

20. On the Anomaly of Travel Time of P waves Observed at Japanese Stations Part(1)

The P-wave travel times to Japanese stations were investigated. Kurile Islands earthquakes gave arrivals earlier than those expected from the Jeffreys-Bullen table. Neither location errors nor reading errors are likely to be the cause of this phenomenon. The early arrivals may be due to a high velocity structure beneath the Island Arc from the Kuriles to Japan. It is found that the upper boundary of this high-velocity structure is dipping toward south west and not shallower than 60km. Its thickness is increasing in the same direction and the lower boundary is not deeper than 400km. This pronounced anomalous structure could not be found in any direction other than that of the Kurile Islands. The seismic waves which travel in this anomalous region are less attenuated than those travelling elsewhere, especially in higher frequency range.|Nihon no kansoku ten made no P-ha no soji o shirabeta. Chishima no jishin wa Jeffreys-Bullen hyo kara kitaisareru yorimo hayai totatsu-jikoku o ataeru. Shino kettei aruiwa yomitori no gosa ga kono gensyo no gen'in towa kangaerarezu, Chishima kara Nihon made no kojyo-retto no shita no kosokudo kozo ni yoru mono to omowareru. Kono kosokudo kozo no jyogen wa nan-seini shitamuki ni katamuiteori, 60km yori mo asaku wa naranai. Kono kozo no atsusa wa onajiku nansei-hoko ni zokashi, sono kagen wa 400 km yori mo fukaku wa nai. Kono ijyo-kozo wa Chishima-retto igai no dono hoko kara mo miidasarenai. Kono ijyo-chiiki o toru jishin no nami wa tokuni koshuha-ryoiki ni oite hokano basho kara kita nami to kurabete gensui ga sukunai

Discrimination between natural earthquakes and nuclear explosions using the Aswan Seismic Network

There are many seismological differences between earthquake and nuclear explosions, but not all of them are observable at large distances or are applicable to every earthquake and explosion. Several discriminations have been checked using the Aswan Seismic Network (ASN) data. Data of 66 earthquakes and 42 presumed underground explosions which occurred in different regions of China, the U.S.S.R., India, Iran, Turkey and recorded at ASN were collected. All data were selected from the NEIC catalogue and EDR reports. It was found that mb: Msas well as mb(1 Hz): mb (2 Hz) work well for events with mb larger than 4.0 from data observed at ASN and obtained from the NEIC catalogue

Discrimination between natural earthquakes and nuclear explosions using the Aswan Seismic Network

There are many seismological differences between earthquake and nuclear explosions, but not all of them are observable at large distances or are applicable to every earthquake and explosion. Several discriminations have been checked using the Aswan Seismic Network (ASN) data. Data of 66 earthquakes and 42 presumed underground explosions which occurred in different regions of China, the U.S.S.R., India, Iran, Turkey and recorded at ASN were collected. All data were selected from the NEIC catalogue and EDR reports. It was found that mb: Msas well as mb(1 Hz): mb (2 Hz) work well for events with mb larger than 4.0 from data observed at ASN and obtained from the NEIC catalogue

State-of-the-art of historical earthquake research in Fennoscandia and the Baltic Republics

We review historical earthquake research in Northern Europe. 'Historical' is defined as being identical with seismic events occurring in the pre-instrumental and early instrumental periods between 1073 and the mid-1960s. The first seismographs in this region were installed in Uppsala, Sweden and Bergen, Norway in 1904-1905, but these mechanical pendulum instruments were broad band and amplification factors were modest at around 500. Until the 1960s few modern short period electromagnetic seismographs were deployed. Scientific earthquake studies in this region began during the first decades of the 1800s, while the systematic use of macroseismic questionnaires commenced at the end of that century. Basic research efforts have vigorously been pursued from the 1970s onwards because of the mandatory seismic risk studies for commissioning nuclear power plants in Sweden, Finland, NW Russia, Kola and installations of huge oil platforms in the North Sea. The most comprehensive earthquake database currently available for Northern Europe is the FENCAT catalogue covering about six centuries and representing the accumulation of work conducted by many scientists during the last 200 years. This catalogue is given in parametric form, while original macroseismic observations and intensity maps for the largest earthquakes can be found in various national publications, often in local languages. No database giving intensity data points exists in computerized form for the region. The FENCAT catalogue still contains some spurious events of various kinds but more serious are some recent claims that some of the presumed largest historical earthquakes have been assigned too large magnitude values, which would have implications for earthquake hazard levels implemented in national building codes. We discuss future cooperative measures such as establishing macroseismic data archives as a means for promoting further research on historical earthquakes in Northern Europe