Figure S5. Phase velocity resolution test with strongly reduced velocities within the ring fracture of the caldera. a) The input structure includes a 6-km wide low-velocity anomaly with 4-s Rayleigh wave phase velocity reduced by 20%. For reference, the observationally estimated phase velocity anomaly at 4 s period is ~15% so this test is using a more severe anomaly. b) The recovered phase velocities from the inversion of synthetic data show that a peak velocity reduction of –17.5% is recovered. Thus, ~85% of the magnitude of the input anomaly was recovered