a–e, Mean elevation (red line) ± 1 standard deviation (grey). Width of the swath profiles is 100 km. The submarine topography and subaerial topography were obtained from the ETOPO1 global relief model78 and the SRTM 90-m digital elevation model21, respectively. To calculate the MME, we first identified the maximum value of the mean elevation along each swath. We then averaged the elevation over the area (black bars) in which the elevation is within 95% of this maximum value. The uncertainty represents one standard deviation of the mean elevation within that area. Dashed horizontal lines indicate sea level. Vertical arrows indicate the position of the trench at subduction zones. Vertical exaggeration is 10.