Micro-seismic survey of Tendaho Alalobeda geothermal field - Processing and Interpretation

In this report the main results related to the activity of the microseismic survey in Tendaho-Alalobeda geothermal area are presented. The contents of this report mainly concerns data processing and analysis, earthquake location and velocity model reconstruction, the elaboration of the network bulletin, the interpretation and informative contribution of microseismic results for the geothermal assessment of the area. Furthermore the present report partially resumes and integrates the activities of instruments installation illustrated in more details in the first report (Tento et al., 2015), hereafter quoted as Rep1. According to ICEIDA (2014) requests, the micro-seismic survey activity in the Tendaho-Alalobeda geothermal area was oriented to: monitoring the microseismicity, investigate its relation to geology and geothermal activity and integrate these results with those obtained from others geophysical investigations planned in the framework of the exploration project. The Tendaho-Alalobeda micro-seismic network (TAMS) was composed by ten seismic mobile stations that were deployed in the study area, it is reported in figure 1. As pointed out in the first report the final TAMS configuration differed significatively from the a priori planned layout due to the logistic, accessibility and, in some cases, geological conditions actually met in field. The final station layout, for the previous reasons, results in a network geometry which quite suitably covers the planned exploration area, but, however, not uniformly as expected in the pre-field planning phase. In particular the network has a lack in its geometry in the southern-western part where was impossible to install any stations due to difficult access to the area. The TAMS network was operated by Institute for Dynamic of Environmental Processes of the National Research Council of Italy (IDPA-CNR) and Electroconsult spa (ELC) in cooperation with Geological Survey of Ethiopia (GSE). Six seismic stations are owned by GSE whereas the remaining four stations belong to IDPA-CNR.