MEXICO CITY ACCELEROGRAPH NETWORK
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BACKGROUND
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On January of 1986, after evaluating the magnitude of the disaster caused by
the earthquakes of September of 1985 in Mexico city, seismic and geophysics engineering experts proposed to CONACyT, to execute several Basic investigations and technological developments useful to mitigate the vulnerability of the urban zone of the valley of Mexico facing this natural danger.
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DISTRIBUTION AND FUNCTIONING
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In 1987 CIRES started the development of the Accelerograph Network of Mexico city (RACM), which counts with 78 equipments: 29 SSA-1 Kinemetrics, originally installed by FICA, and 35 DCA-333 terratech y 7 underground sensors. In 1997, 100% of the Terra Technology equipments were renovated with the digital recording system RAD-851; developed by CIRES to assure the function of this technological resource and to give continuity to its accelemometric measurement service.
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Distribution of the stations of the RACM
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Examples of typical stations of the RACM
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With RAD-851 system, in 1997, CIRES managed to renovate all of the strong motion recorders DCA333, after the manufacturer stopped its fabrication in 1995, giving continuity to the recording of the earthquakes that affect to Mexico valley.
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The strong motion recorders of RACM, renovated with RAD-851 system, register the information with a PCMCIA card with capability to keep a top of 34 minutes of data. They count with adjustable pre-event memory to record 58 seconds before the earthquake and post-event until 100 seconds after the moment when the acceleration of the earthquake is less big than the selected minimum triggering threshold.
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Card RAD-851
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To get the accelerogram register site, a portable computer is used. It also permits to check and/or to change the
operation parameters and to verify the sensor's calibration. Some of these stations have got telephonic line and are interrogated by MODEM.
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DIFFUSION
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The seismic accelerograms are divulged to promote activities of research about design and seismic risk factors, by publishing bulletins, presentations of congresses and seminaries, also among the institutions that help with the preservation and the up-to-day bringing of the Mexican strong Motion Earthquake Data Bate, It has been edited with the support of the Sociedad Mexicana de Ingeniería Sísmica (SMIS), volume 1 and 2 in CD-ROM format. These disks gather the results of different Mexican institutions dedicated to seismic information recording, and present 13,545 accelerograms obtained between 1960 and 1999.
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RACM Report
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Also CIRES divulges a bulletin delivered to the Public Work Departmet of Mexico city government in less than 24 hours after an earthquake is felt in Mexico valley. Furthermore, it hands in a bimestral report of the service, operation and conservation activities done in every RACM station and also the strong motion data that has been obtained each period. One of the main objectives of CIRES is to keep all of the results available to the investigators and seismic engineering specialists in Mexico and abroad.
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ACCELEROGRAPH INFORMATION HEAP
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The continuity of RACM service, until June of 2006, has permited to pick up 3,512 accelerographs, recorded during the effects of 143 earthquakes. This heap of acelerographs keeps more than 124 hours of accelerometric information.
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ACKNOWLEDGES
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We thank to the authorities of Public Works Department of Mexico city government for the sopport given to the activities of operation and keeping the RACM.
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