资源环境科技发展态势分析平台

Variations in stress drops of earthquakes associated with the April and May 2015 eruption of Axial Seamount, on the Juan de Fuca Ridge, suggest a reduction in crustal strength as a result of the eruption. Seismicity during the inflation and deflation periods was well‐recorded by ocean bottom seismometers located within and along the caldera. We use these nearby recordings and an empirical Green’s function spectral ratio method to obtain corner frequencies for stress drops of earthquakes on caldera ring‐faults. We find stress drops from 0.6 to 43 MPa for 423 ring‐fault earthquakes (1.6 ≤ M _W ≤ 3.6), and average stress drop 2 times higher during the inflation period (6.4 MPa) prior to the eruption, than during the subsequent deflation (3.2 MPa). Stress drops also correlate with spatially varying shear wave speed, possibly reflecting a region of pervasive cracking in the northern caldera.