Virginia TenorioINETER, Dirección General de Geofísica

Managua, Nicaragua

Calderas of Nicaragua - Activity and Monitoring

Foto: Open vent at Masaya volcano

Nicaraguan Volcanic Chain

Monitoring Systems

- Visits to active craters in regular periods- One seismic station near the active crater and main volcanic centers (and not active)- Seismic Networks at most active volcanoes- Permanent MiniDOAS, mobile miniDOAS- GPS sites, regular campaigns

Telica VolcanoMay, 2011

San Cristobal VolcanoApril, 2006

Height: 859 m

Activity: 1835 - Huge eruption from central crater, !!Little damage due tolow population densityType of Eruption: Plinian-PhreatomagmaticVEI: 5

Hazard Index: 14

Recent activity: Seismicity, 2002

Monitoring: Seismic broad band station

Cosigüina Caldera

September 2002 - Strong seismic activity near Cosigüina volcano.

First mayor activityknown in 27 years of the existence of the Nicaraguan seismic Network.

Also, in the historicrecords there appearsVery little information on strong seismic activity like in septiember, 2002

Cosigüina Caldera – recent activity

Typical for volcano.-seismic activity (VT):- The events ocurred in various pulses- The pulses liberated similar amounts of seismic energy- Ocurred many events with similar magnitude 3 < M < 4- The maximum magnitude increased 2 times- The distribution of energy was unlike tectonic activity

Cosigüina 2002 - Magnitude vs. time

ConclusiónAccording to the formula of R. White for intruded volume from seismic moment, the volume of magma would be roughly about 500,000 m3

This didn’t seem like nearly enough to reach the surface.

We remained on alert for further seismic activity or any volcanic activity but none followed.

Height: 1,100 mActivity: Eruption in centralcrater Type of Eruption: StrombolianaVEI: 2Hazard Index: 11History: 10 eruptions since 1524Actividad actual:Seismicity, Fumaroles T>700 C

MomotomboVolcano(remanent of Monte Galan Caldera)

Momotombo Volcano

Frequent seismic swarmsExample: Seismicity of June, 2000

Hazard- Earthquakes - Landslides- Lahars- Ash fall- Lava flows- Catastrophic Explosions

Visit to the crater

Height: 420 mType of Actividad: Eruption of central craterType of Eruption: PlinianHistory: Plinian 12, 6 , 2 thousand years ago Recent actividad:Seismicity Swarms

Volcano hazard- Ash fall (3 m in Managua)- Pyroclastic flows –> Managua!

- Lahars, Earthquakes

ApoyequeCaldera

M=5.0, Jan 2001.Thermal springs

Managua – Volcanic Hazard

Managua (1 million)

Apoyeque Caldera

Apoyo CalderaMasaya

Caldera

Tiscapa volcanoNejapa-Miraflores Lineament

(Maars)

Masaya (100 000)

Cd. Sandino (80 000)

Height: 635 mType of Activity: ExplosiveEruption Type: PlineanLast eruption: 22 y 17 thousandyears agoRecent activity:Frequent seismicswarmsDestructive earthquake M=5.2, July 2000.0.5 m displacement verticalThermal springs . High SO2, CO2. Peoples died

Apoyo Caldera

Santiago CraterMasaya CalderaHeight: 635 m

Type of Activity Violent crisis due to degasificationType of Eruption: Hawaiian StrombolianaVEI: 2Hazard Index: 10History: Very Active since 1720Recent Activity:Lava LakeSO2 5000 t/day, sporadic explosions

Volcanic hazard- Lava flows- Lahars

Huella de Acuahualinca

MasayaVolcano

Volcanic hazard- Pyroclastic flows- Ash fall- Gas column- Sporadic explotion

Explosion. April, 2001

Volcanic hazard- Seismic events

Destructive Earthquakes between Apoyo and Masaya calderasJuly, 2000: Two main events of magnitud 5.4 and 5.2 with one day time difference.

One minute before,the Earthquake occurred

Destructive Earthquakes between Apoyo and Masaya calderasJuly, 2000: Two main events of magnitud 5.4 and 5.2 with one day time difference.

M=5.4

foreshock

M=5.2

M=5.4

Conclusions• It appears that calderas are exceptionally stable volcanic

structures, in the sense that they can accommodate a large amount of unrest, especially occasional intrusions, without producing eruptions.

• It appears that they can accommodate significant purely tectonic activity as well, that does not affect the volcanic system in any visible way.

• It also appears that adjacent calderas may be connected by tectonic structures and transfer stresses from one to the other without transfering any significant stress to the magma?

Nicaraguan Civil DefenseMonitoring and Operations

Center Discussion on EmergencyPlans for Managua

Gen. Perezcassar and V. Tenorio

Rapid automaticinformation system for

seismic eventswithin 2 minutes

Volcano Disaster Plans for Managua

GRACIAS