Converted-wave recorded in surface microseismic monitoring This work shows the results obtained from an arrival that comes immediately after a P-wave obtained from a surface monitoring. These recordings belong to a fracturing work of an unconventional hydrocarbon deposit from which it would be very useful to obtain as much information as possible from the data collected. In this second arrival it is possible to observe characteristics that make us suppose that it is a shear S-wave. Given that these recordings belong to a microseismic study, and that they were acquired using only vertical geophones, it is not possible to assure the nature of this arrival in a preliminary study of particle movement. If the recordings were of three components, it would be possible to discriminate between these second arrivals studying the polarization by composing the horizontal and vertical components. The following has been observed: Determination of average velocity, amplitude analysis according to offset and azimuth. The feasibility of recording S-waves with vertical geophones was posed as well as the benefits of counting with S-waves recordings at perforation stage. The use of this secondary event has been proposed for further study