## 3 Results
### Pockmark Field
#### 3.1.4 Pockmarks Venting  
In the seismic profiles, the pockmarks show acoustic characters indicative of their formation mechanism and activity. Profiles have shown that the common pockmarks are U- or V-shaped and abruptly interrupt the low amplitude internal reflections of the SS I (Figures 12, 13 and 14a). Some of them have a flat bottom and resemble a truncated cone. In many cases, the pockmarks were recorded with lateral reflections overlapping each other, creating synclinal or bow-tie structures, suggesting very steep slopes and narrow floors at the pockmark sites (Figure 13). Steep slopes seem to be affected by gravitative mass movements, as indicated by small, detached blocks that partially infill the pockmarked floor (Figures 12 and 13b). The floors of the pockmarks are always in the upper seismic sequence (SS I), as all pockmarks terminate above the base of the Holocene unit. On the profiles of the pockmarks, the ATZs are often present below their floor, suggesting that the sediments below the pockmarked floor contain gas and thus the potential for a continuous supply of gas from the Pleistocene/Holocene interface upwards to the pockmarked floor (Figures 12, 13 and 14a). In some unit pockmarks, the continuation of the ER is abruptly interrupted just below the pockmarks floor (Figure 13b,c). This interruption of ER proposes gas escape through a weakness zone and, thus, the formation of small pockmarks. In some cases, a zone with a transparent acoustic character is observed below the pockmark floors and at their sidewalls (Figure 13c). The recording of this acoustically transparent zone probably indicates that: (i) the escape of fluids was not limited only by the bottom of the pockmark but also from the entire surface of the pockmark walls and (ii) the gas seepage was vigorous and disturbed the structure of the sediments. Similar processes have been reported by [39] in a pockmark of the field. Figure 12: High-resolution seismic profile showing numerous normal and composite pockmarks, as well as the biggest pockmark in the field (right), located near the southeastern part of the study area. ATZs are found immediately beneath the majority of medium- to large-sized pockmarks. Above one of the pockmarks, a gas flare is recorded. The HOL/PL boundary is partially visible when the gas-related reflections in the upper seismic sequence disappear (PM: pockmark; ER: Enhanced Reflector; ATZ: Acoustic Turbid Zone; IGP: Intrasedimentary Gas Plumes; GFI: Gas Flare; DB: Detached Block; HOL/PL: Holocene Pleistocene boundary; TWTT two-way travel time). Figure 14: (**a**) High-resolution seismic profile showing a gas flare over a pockmark (ER: Enhanced Reflector; ATZ: Acoustic Turbid Zone; GFl: Gas Flare; HOL/PL: Holocene Pleistocene boundary; TWTT two-way travel time); (**b,c**) slant range uncorrected 400 kHz side-scan sonar sonographs showing gas flares (white arrows indicate their position) in the water column rise from the centre of the pockmarks (horizontal lines every 20m). Figure 13: High-resolution seismic profiles showing (**a**) pockmarks with narrow floor on the north sector of the field near AT.F; (**b**) two pockmarks, a composite (right) in which the Acoustic Turbid Zone is close to the seabed and a Detached Block is recorded at the sidewall and a normal one (left) where ER and ATZ are interrupted below it; (**c**) a large pockmark (left) where a transparent acoustic character (indicated by red arrows) is observed under its floor and; an Intrasedimentary Gas Plume (right) located between two minor synthetic normal faults and a small pockmark (centre). (PM: pockmark; ER: Enhanced Reflector; DB: Detached Block; ATZ: Acoustic Turbid Zone; AT:G Asia Triada Fault; HOL/PL: Holocene Pleistocene boundary; TWTT two-way travel time). Few acoustic anomalies consisting of straight and inclined reflections were observed in the water column (Figures 12 and 14). These disturbances are located directly above pockmarks and have been recorded both on side-scan sonar sonographs and seismic profiles (Figure 14).