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Abstract

 

The Nicaraguan Seismic Network registered in February, 1998, a number of 160  seismic events. The majority of them were located in the subduction zone off coast of the Pacific Ocean. Seismic events occurred also in the volcanoes San Cristóbal, Telica, Cerro Negro and Momotombo.

The seismic activity of  San Cristóbal volcano which had calmed down in Januarry, 1998, presented a sudden increase in February reaching a new maximum, within a few days. The character of this seismic activity has changed. The tremor which before was practically continuous occurs now in form of fluctuations or events. These events are following one to another in very short time distances, so that the automatic detection routines records several hundred events per day. 

The seismic activity at  Telica volcano  maintains its high level of more than 100 events per day.

A new seismic station was installed at the rim of Tiscapa Lagoon, a volcanic crater lake in the center of Managua.

The Nicaraguan Seismic Network counts now with 20 telemetric seismic stations, 10 of them located in volcano complexes. The data are digitally recorded and processed at Managua data center, which in turn has also a set of seismometers . Any seismic event detected by the data acquisition routine is processed regularly within a short time by the seismologist on duty. In case of a strong event the system emits an acoustic signal and the seismologist determines immediately the parameters of the event and sends within minutes a report to the Nicaraguan authorities and the mass media. Any unusual behavior of the seismic signal in the volcanoes would also be reported to enable preventive measures against the negative effects of dangerous phenomena in the volcanoes (beginning eruption, land slides, strong degassing).  

The Monthly Bulletin is published in the first days of the following month, after having revised the preliminary data. It is distributed in Nicaragua to governmental organizations and mass media, in Central America to cooperating institutions in Guatemala, El Salvador, Honduras, Costa Rica, Panama. Furthermore it is sent to several cooperating institutions in South America, North America and Europe. Phase data and waveforms can be obtained writing to the address on the front page.