Locating Scattered Energy in Vogtland's Earthquake Swarm Source Area through Double 3D-Array Beamforming and Inter-Event Coda Correlation Imaging (D3D)

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We aim to detect and quantify the characteristics of crustal scatterers located within and around the source area of the West Bohemian / Vogtland region from transient Earthquake signals. The quantification of scattering strength and its dependence on variable angles provides insight into the nature of scatterers as structural elements and their possible physical relation with the postulated ongoing deep fluid flow. We will exploit the information from the observation of weak coda phases at multiple arrays. In order to improve the high frequency content of the observations we will install a deep borehole array beneath a classical surface array for the continuous observation of transient signals as well as the ambient vibration wave field. This 3D-array installation (receiver array / RA) will be used in combination with the reciprocal 3D array recording geometry known as source array (SA) for consistently locating weak scattered energy close and within the volume of earthquake swarm generation. Furthermore we propose to use a source to source coda correlation technique to generate an inter-source Green’s function database. This database will be derived from existing swarm data in recent years but then further augmented by observations at the newly deployed installations. It will be used to derive the velocity structure in the source volume of the swarm region and will allow investigating not only the spatial but also the temporal character of velocity anomalies as possible cause for swarm triggering or indications for fluid pathways in depth.