Short-period ocean bottom seismometer (SPOBS) active-source data, Lesser Antilles arc, acquired during James Cook cruise JC149 - Leg 3 (2017) as part of the UK NERC VOILA experiment

In this active-source part of the VOILA (Volatiles in the Lesser Antilles) experiment, during RRS James Cook cruise JC149 Leg 3, short-period ocean bottom seismometers (SPOBS) were deployed on the incoming plate and airguns from the James Cook vessel were fired to them. The OBS instruments were deployed in a roughly north-south orientation along strike, approximately 300-400km east of the trench and their positions were calculated by acoustic ranging. The data files presented here contain the three geophone components (X,Y,Z) and Hydrophone (H) in standard SEG-Y format. Note that Station 214 has only the H component. The number of files for each component is as follows: H (97 files), X, Y, Z (96 files each). In total there are 97+(96x3)=385 files. For the file names, "rl" means relocated and "HM" means Header Manipulation. The header manipulation involved three aspects: (1) Keep only shots that are on the 2-D seismic profile. The first shot on profile for Line 2 is shot number 80 while the first shot on profile for Line 3 is shot number 50. So the shot point number for the Line 2 SEG-Y file starts from shot 80 onwards while for Line 3 it starts from shot 50 onwards. (2) Modify receiver x and receiver y based on OBS relocation. See the associated ASCII relocation documents called OBS_relocations_line_2_3_latlon.txt and OBS_relocations_line_2_3_utm.txt. (3) Assign source-receiver offset to each trace for shots north of the OBS relocation as negative, while any source-receiver offset for shots south of the OBS location are assigned as positive. Navigation coordinates in the headers are in UTM meters, zone 21N. The goal of this active-source portion of the VOILA experiment was to assess the geological structure and state of hydration of the subducting plate. The cruise report and other details may be accessed here https://www.bodc.ac.uk/resources/inventories/cruise_inventory/report/16390/. The chief scientist on James Cook cruise JC149 Leg 3 was Jenny Collier (Imperial College London), and funding for the VOILA experiment was provided through a NERC multidisciplinary consortium project called Volatiles in the Lesser Antilles - VoiLA, supported by NERC award NE/K010743/1.