DEEP SEATED FAULTING BENEATH THE FLUID VENT FIELD LOCATED OFFSHORE OF MANZANILLO: EVIDENCE FROM MULTICHANNEL SEISMIC REFLECTION DATA
Multibeam bathymetric and seafloor backscatter data has imaged a large seafloor dome (15 km diameter with >400 m relief) on the continental slope, 50 km SW of Manzanillo, Mexico [Bandy et al., 2020, 2024]. The apex of the dome is located at 18 deg 44 min N, 104 deg 38 min W, at a water depth of 600m. An extensive fluid vent field is associated with the dome at water depths of <1 Km, and is delineated by its high backscatter strength indicative of rough seafloor lacking a significant sediment cover. The field is comprised of numerous circular vents of varying size ranging up to 300 meters in diameter with up to 20 meters of relief. Several elongated low-seafloor-reflectivity areas emanate from the largest vents suggesting that a large amount of sediment/debris is also being vented. The origin of the seafloor dome has been proposed to be related to a subducting seamount, although the seamount has yet to be imaged. The origin of the vented fluids has been proposed to be the fluids flowing along the underlying mega thrust contact between the overlying Jalisco Block and the underlying Rivera Plate [Bandy et al., 2020]; which if correct, has important implications for the origin of the great 1995 Jalisco EQ whose epicenter is located just landward the vent Field (i.e., just downdip along the mega-thrust).
In this study, a 96 channel multichannel seismic reflection profile previously obtained during the CORTES-P96 campaign of the R.V. Hespérides [Dañobeitia et al., 1996] which crosses the dome is analyzed to determine if it supports the presence of the previously proposed subducting seamount and deep seated faulting beneath the vent field. Several deep seated faults are clearly imaged in the data. However, the presence of a subducting seamount remains uncertain.
References:
Bandy et al. (2024), Cartel, Reunión Anual UGM 2024.
Bandy et al. (2020), Presentación, Reunión Anual UGM 2020.
Dañobeitia et al. (1996), EOS Trans AGU, 78 (49) 565-572.