Seismic clusters

The seismic clusters are phenomena that happen in the Volcanic Chain and the mountainous zone of Nicaragua. They are characterized by a great amount of earthquakes with similar magnitudes. They can happen during days, weeks or months. They begin with a greater amount of small earthquakes, followed by one or several earthquakes. In opposition to the type of seismic activity that consists of a greater earthquake followed by a chain of much more small retorts that the main event.

a) Seismic clusters, 1998

January:
The 16 of January to 09:02 p.m. local time was felt an earthquake in the South part of the fault Brotherhood, the magnitude of the earthquake was of 3,3 scale Richter.
Also day 17 several earthquakes in he himself sector of the zone of Brotherhood were felt

March:
The day Domingo 01 of March of 1998, to 08:51 p.m. local time (02: 51 UT), the Seismic Network of Nicaragua hard registered a located earthquake in the sector of Momotombo volcano. The magnitude was of 4,1 (Richter), and ML=4.6. The earthquake was followed of a seismic cluster that lasted of two days. The seismic network registered more than 60 retorts than in his majority they were located to the South of Momotombo volcano. The Maxima intensity was of I SAW degrees in the Scale of Modified Mercalli.

April:
Day 31 of March to 10:05 p.m. local time, the Seismic Network of Nicaragua registered a series of earthquakes from low magnitude to the East of the city of Masaya. This series of earthquakes followed until the 02 of April, 1998.

Of this cluster 2 events were felt by the population. First it was registered the 01 of April, to 11:44 p.m. local time, the magnitude was determined in 3.2 scale Richter. The second was felt the 02 of April, 1998, to 11:17 A.M. local time, the magnitude was of 3,3 scale Richter. In Masaya an Intensity of V MM was considered (Scale of Modified Mercalli).

Day 10 of April:

It happened another seismic cluster. No earthquake was felt by the population. The magnitude oscillated in 1.8 to 3,2 in scale Richter. The depth of the seismic centers was between 2 and 12 kilometers.

May:
Day 06 of May to 03:42 A.M. local time, the Seismic Network of Nicaragua detected an earthquake from Mc=3.4 magnitude to the East of the city of Masaya. This it was the beginning of a seismic cluster that lasted two days. 34 microearthquakes were entered of which 12 were located. Two events of this cluster were felt by the population in Masaya and the environs. The magnitude of the earthquakes oscillated between 2,7 and 3,6 in scale Richter. The rank of hypocentral depth was determined between 1,1 and 7,6 kilometers. The Maxima Intensity of the greater event was determined in IV in scale of Modified Mercalli.

September:
Day 01 of September a seismic cluster in Masaya volcano was registered, with more than 10 microearthquakes, without being located; one assumes that these events were of smaller Magnitudes to the 2 degrees (Richter).

Day 26 of September another seismic cluster in Masaya volcano was registered. In all the month 64 microearthquakes were registered. It is mentioned that at the end of September the conduit at heart of the crater was opened again and brilliance is observed, this conduit was prevented in November of 1997.

October:
The day Domingo 18 of October, to 07:31 a.m. local time, an earthquake (magnitude 3,4 Richter) strongly felt by all the community of Ticuantepe was registered, most of neighboring Managua and towns; this it represented the beginning of a seismic cluster that lasted 18 days, that include the first four days of November. To 08:20 a.m., a second earthquake was registered whose magnitude was greater to first (4,0 Richter) and produced alarm between the population. The activity continued with great amount of microearthquakes but soon it decayed quickly. The epicenters concentrated next to the town of Ticuantepe to 14Km to the Southwest of Managua and western edge of the boiler of Masaya.

A total of 390 microearthquakes was entered during the period from the 17 to the 31 of October, of which it was possible to locate 118 with magnitude greater than 1.9. The first 36 hours of this cluster were critics, representing the more 90% of the total of located events, waking up alarm between the population near the epicentral area.

The earthquakes of this cluster were characterized for being of low magnitude, minor to the 4,0 degrees in the scale Richter and depths smaller to 15 km, the events located to smaller depths of 8Km of depth.

b) Seismic clusters, 1999

April:
Day 02 of April to 10:22 p.m., local time, the seismic network registered a strong earthquake with epicenter in the Gulf of Fonseca who had the magnitude MILILITER of 5.6. Half an hour later, to 10:53 p.m. it happened another strong earthquake (ML=4.8) in he himself place. Followed a series of retorts took place.

To 4:10 A.M., local time, it happened an earthquake of greater magnitude, than it had magnitude ML=5.8. This event and many of their premonitors and retorts felt in extensive areas of Nicaragua, Honduras and El Salvador. In Tegucigalpa, the earthquake caused great scare. There were no disastrous effects. Salvadoran authorities reported damages in the Mangueare island located in the Gulf of Fonseca, near the epicenter of the earthquake, more than one hundred houses were affected. In Potosí an intensity calculated I SAW in the scale of Mercalli.

July:
Near volcanos Black Hill, the Batteries and the Hole two seismic clusters happened in this month; first from the 01 to the 03 and the second of the 27 to the 28 of the month, registering itself in all the month 94 microearthquakes. locate 25 earthquake with magnitude between 2,3 and 3,4 in scale Richter. The depth of the events oscillated between one and five kilometers. The first cluster was located to the East of the volcano the Hole. The second the Hole was located to 1km to the North of the volcano. In this cluster one registered the 27 to 01:49 a.m., local time, an earthquake relatively hard that had the magnitude of 3.6. This earthquake was felt by the settlers who live in the neighborhood of the volcano Black Hill.

Day 26 type cluster happened an unusual activity in the sector of San Rafael of the South. Many events were only felt by the settlers of this sector. The seismic network detected only the strongest events. Most of these earthquakes they are of low magnitude. The 26 of Julio to 10:04 p.m., local time, an earthquake was registered that was felt by most of the inhabitants. Its magnitude was of 2,9 in scale Richter. The event happened to a depth of 6 kilometers.