Figure 1.

Conceptual cross sections showing structure of fault-controlled methane seepage at convergent plate boundaries. (a) In accretionary active margins, methane is frequently released at mud volcanoes, which are sourced from thrust faults splaying off from the subducted plate interface (Nankai subduction zone; adapted from Park et al.³⁰). (b) In erosional active margins, methane is often released via normal faults that die out near the basal subduction interface and form seabed seepage structures such as pockmarks and authigenic carbonate mounds and associated gas pipes (Costa Rica-Nicaragua subduction zone; adapted from Ranero et al.¹⁸). This figure was generated using Adobe Illustrator CS3 (https://www.adobe.com).