Muography (muon radiography) is a new geophysical technique that allows investigation of inner structures of an ediﬁce with a very detailed spatial resolution. It has been recently used for several volcanoes and different geoscientiﬁc targets. In 2011 Tanaka et al. succeeded to ﬁnd hidden ancient seismic faults. In 1949 there was a volcanic activity of the Cumbre Vieja, La Palma, Canary Islands, Spain and a 1km-long fault suddenly appeared during the active period. The fault might be the sign of a large scale land collapse. In order to get additional informa- tion, investigations by several geophysical exploration techniques are needed. We consider that muography can be applied to study the shal- low part of the fault and it can clarify some important parameters: the bulk density, the width of the low density zone, and the depth. Previous investigations allowed detecting two ancient seismic faults that have 20m-wide mechanically fractured zone consisting of highly damaged rocks. The 1949 fault might be the result of large scale land slide and the slide length might be just a few meter. Therefore the expected width of the fault is only a few meter. In order to detect such narrow fault, the muon detector should have as high spatial resolution as possible. In ad- dition, it is difﬁcult to get continuous power supply near the fault. Nu- clear emulsions are a kind of photographic ﬁlms that have high sensitivity for high energy charged particles. They also have high spatial resolution for high energy muon paths and do not need any power sup- ply to be operated. We placed an emulsion detector having 0.19 m2 effective area near the 1949 fault. The exposure started on January 2014 and lasted 106 days. All the emulsion ﬁlms were developed and they are under analysis. We also estimated the expected performance of this test exposure. Assuming a very simple model, we evaluated the detectable region as a function of the low density zone width and of the depth from the ground surface as well.
|Titolo:||Muography of 1949 fault in La Palma, Canary Islands, Spain|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||4.1.1 Proceedings con DOI|