American Academic Scientific Research Journal for Engineering, Technology, and Sciences
Abstract
The Nyamulagira volcano is located in the western branch of the East African rift (bordered by a many faults) and is often characterized by fissural eruptions of very potassic fluid lavas. These eruptions are preceded by a variety of pre-eruptive low-frequency seismic signals. Hybrid earthquakes are one of these signals. In this short communication, we collected seismic data over a four-year period from 2011 to 2014 (a period during which two eruptions Were observed at Nyamulagira: one in November 2011, another in June 2014) at the station of Rusayo and Kibumba which are very close to this volcano (about 10 km), with the aim of analyzing the characteristics of hybrid earthquakes as well as the volcanic activity that they accompany. We found that these earthquakes are characterized by a high frequency occurrence ranged between 3 and 10 Hz, they often occur in swarms and located at shallow depths between 0 and 5 km. They are interpreted as being related to a movement of breakage of rocks by fluids and generally in weakness areas that are the emplacement of cracks and faults of the East African Rift. They therefore accompany magmatic intrusions and precede most of the fissural eruptions observed at Nyamulagira volcano. These hybrid earthquakes are used as indicators of imminent eruptions and their observation is an effective tool for monitoring the Nyamulagira volcano
