Fig. 3: Cross section of Chain transform fault.

Vertical distribution of 89 events determined by moment tensor inversion (circles). Panel a shows the eastern part of Chain, focusing on the Eastern Large Flower Structure (ELFS), defined by the rectangle in b. The depth determination quality (Q1 and Q2) is indicated as dark and light circles, respectively. Mean vertical uncertainties are 3 km for Q1 events (black vertical error bars) and 6 km for Q2 events (gray vertical error bars). The events located deeper than the 600 °C isotherm from simple thermal models (dashed blue lines in panels b and c) are highlighted with a red dot. The horizontal blue lines denote the location of the transpressional flower structures, whereas the vertical shaded bars indicate the asperities (A1, A2), separated by barriers (B1, B2, B3). Depths are below sea level. a P-wave refraction model from the active source survey at the eastern part of Chain, beneath the ELFS (see Methods; Supplementary Data 1). b S-wave wave velocity model³⁵. The dashed blue isolines (and numbers in blue boxes) indicate the thermal structure as determined by the prediction from a half-space cooling model for a transform region, assuming a half-spreading rate of 16 mm/yr. c Thermal structure predicted by the S-wave wave velocity model shown in b using the relationships of Stixrude and Lithgow-Bertelloni⁴⁷. For additional approaches and assumptions for the thermal calculation please see Methods, Supplementary Fig. 2.