Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

424 Kezin Qua History of Chinese Seismic Stations. It is divided into 3 volumes and the firstvolume contains three parts: Part 1 concerns those basic stations participating ininternational exchange of seismic data; Part 2 concerns those not yet participating ininternational exchange; Part 3 concerns digital seismic stations. The second volumeis about telemetered seismic networks; and the third volume is about networks oflocal stations. Part 1 of the first volume will be published by the end of 1985.5. Timing SystemIn 1954, an astronomical clock with a second pendulum was commonly used inthe seismic stations on the China mainland. To improve the time service, seismicstations built since 1958 were equipped with quartz clocks. From 1980 onward,the seismic stations that are included in the Preliminary Seismic Report of ChineseStations have been using Type 768 clock stations or the AST system; and furthermore,it was stipulated that all seismic stations throughout the entire country use"BJUTC" instead of "BJUT1" from 1980 on.6. Results and Services of Seismic ObservationsThese seismic stations are all under the unified administration of the State SeismologicalBureau of China. The Institute of Geophysics of the State SeismologicalBureau is technically in charge of the quality examination of seismic records fromthe standard and basic seismic stations, analysis and compilation of seismologicalreports, microfilming of seismograms, management and exchange of seismic informationand data, and improvement of observational techniques and equipment atthe seismic stations. Local seismic stations under the administration of the provincialseismological bureaus (subordinate to the State Seismological Bureau) compilelocal seismic reports and seismic catalogs.Seismograms and seismological reports are important observational results fromthe seismic stations. On the China mainland, seismograms recorded with some ofthe main types of instruments, such as SK, 763, Type 62, and others, are totallypreserved whether or not they contain seismic events; but those seismograms withoutevents (e.g., seismograms recorded with Type 513 or DK-1) are not preserved.Every station compiles its own seismic reports and every network compiles its ownseismic catalogs monthly. The Institute of Geophysics of the State SeismologicalBureau then compiles the Preliminary Seismological Reports and Annual SeismologicalReports of Chinese Seismic Stations. These two reports are not only intendedfor use in China, but also for international exchange. We have already establishedexchange relations with 71 institutions in 49 countries or areas.Recently, the number of persons who want to use our seismograms has increasedgreatly. To increase the rate of utilization of the seismograms and to ease theproblems encountered in their management and storage, we are making microfilms ofthe seismograms and have started a microfilm exchange with World Data Center-Afor Solid Earth Geophysics, Boulder, CO, USA.Special emphasis was put on records from the 24 basic stations, including Sheshan,Lanzhou, Nanjing, Beijing, and Dalian. All seismograms from these basicseismic stations since 1969 were microfilmed, and microfilm copies of 39,324 threecomponentseismograms were sent to World Data Center-A.