Estimate of the stress field in Kilauea's South Flank, Hawaii

Abstract

SUMMARY We estimated stress and seismic strain tensors for the Kilauea volcano's south flank. The stress orientation inversion and the seismic strain calculation were performed using fault-plane solutions. The principal stress and seismic strain directions are approximately uniformly distributed in space and time during the interval covered by the data. However, the 01,03 plane is approximately orthogonal to the plane. Therefore, a weak layer may exist beneath the south flank. o1 has a plunge of 59 and an azimuth of 152, with a 10 95 per cent confidence range. We also developed a stress magnitude inversion to estimate magnitudes of boundary and interior stresses. In this inversion, the principal stress directions were taken as constraints in the seismic volume, and surface geodetic observations were used as data. The maximum magmatic pressure in Kilauea's rift zone is about 160 MPa. The direction of o1 can be interpreted as the superposition of hydrostatic stress (pgh) and magmatic pressure. Without the constraint imposed by the direction of ol, the estimated pressure is only 60 MPa. The distribution of magmatic pressure may be similar to that of pgh. In contrast, the upper rift zone may be in tension. The shear stress in the rift zone is about one order of magnitude smaller than the maximum compressive stress, supporting the interpretation of magmatic flow as fluid in dikes or channels. The combination of stress orientation inversion, seismic strain calculation, and stress magnitude inversion performed in this study provides a means by which to estimate the stress state in seismic areas.