THE FEBRUARY 1993 KILAUEA EAST RIFT ZONE DIKE INTRUSION REVEALED THROUGH INSAR

Open Access
Author:
Moore, Sarah Catherine
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 01, 2017
Committee Members:
  • Christelle Wauthier, Thesis Advisor
  • Peter LaFemina, Committee Member
  • Charles Ammon, Committee Member
Keywords:
  • Boundary Element Method
  • Inversion
  • Static Stress Change
  • Nonlinear Inversion
Abstract:
Passive intrusions make forecasting and risk assessment difficult since they are not preceded by inflation nor by large increases in seismicity. The February 1993 dike intrusion in the East Rift Zone (ERZ) of Kīlauea Volcano, Hawaiʻi, was recognized from tilt and seismic data, but the ground-based geodetic data were too sparse to constrain the characteristics of the intrusion. Analysis of Interferometric Synthetic Aperture Radar (InSAR) from the Japan Aerospace Exploration Agency (JAXA) JERS-1 satellite reveals ~30 cm of Line-of-Sight (LOS) displacements occurring near Makaopuhi Crater in the middle ERZ of Kīlauea. We model this deformation signal as a subvertical dike using a 3D-Mixed Boundary Element Method (3D-MBEM) paired with a nonlinear inversion algorithm to find the best-fit model. The best-fit dike model is located just to the west of Makaopuhi Crater and within 100 m of the surface. The best-fit model dike is ~1.3 km in length by ~2.7 km in width, strikes N50W, and has a total volume increase of ~7.4 x 106 m3. Additionally, a post-intrusion interferogram from JERS-1 was analyzed. The best-fit model for the 1993-1997 period consists of opening of the deep rift zones beneath the Southwest Rift Zone (SWRZ), ERZ and the summit. The dike-like opening beneath the rift zones ranges from depths of 3-12 km and has an average opening of about 0.5 meters. A sub-horizontal detachment fault is connected to the seaward side of the vertical dike-like source to mimic the decollement. We classify the 1993 dike intrusion as a passive intrusion similar to those that occurred in 1997 and 1999. Passive intrusions lack of precursory inflation at Kīlauea’s summit and the likely triggering mechanism is persistent deep rift opening combined with seaward motion of the south flank along a basal decollement.