TY - JOUR T1 - Asymmetric shallow mantle structure beneath the Hawaiian Swell-evidence from Rayleigh waves recorded by the PLUME network JF - Geophysical Journal International Y1 - 2011 A1 - Laske, Gabi A1 - Markee, Amanda A1 - Orcutt, John A. A1 - Wolfe, Cecily J. A1 - Collins, John A. A1 - Solomon, Sean C. A1 - Detrick, Robert S. A1 - Bercovici, David A1 - Hauri, Erik H. AB - We present models of the 3-D shear velocity structure of the lithosphere and asthenosphere beneath the Hawaiian hotspot and surrounding region. The models are derived from long-period Rayleigh-wave phase velocities that were obtained from the analysis of seismic recordings collected during two year-long deployments for the Hawaiian Plume-Lithosphere Undersea Mantle Experiment. For this experiment, broad-band seismic sensors were deployed at nearly 70 seafloor sites as well as 10 sites on the Hawaiian Islands. Our seismic images result from a two-step inversion of path-averaged dispersion curves using the two-station method. The images reveal an asymmetry in shear velocity structure with respect to the island chain, most notably in the lower lithosphere at depths of 60 km and greater, and in the asthenosphere. An elongated, 100-km-wide and 300-km-long low-velocity anomaly reaches to depths of at least 140 km. At depths of 60 km and shallower, the lowest velocities are found near the northern end of the island of Hawaii. No major velocity anomalies are found to the south or southeast of Hawaii, at any depth. The low-velocity anomaly in the asthenosphere is consistent with an excess temperature of 200-250 °C and partial melt at the level of a few percent by volume, if we assume that compositional variations as a result of melt extraction play a minor role. We also image small-scale low-velocity anomalies within the lithosphere that may be associated with the volcanic fields surrounding the Hawaiian Islands. VL - 187 UR - https://doi.org/10.1111/j.1365-246X.2011.05238.x ER - TY - JOUR T1 - Mantle P-wave velocity structure beneath the Hawaiian hotspot JF - Earth and Planetary Science Letters Y1 - 2011 A1 - Wolfe, Cecily J. A1 - Solomon, Sean C. A1 - Laske, Gabi A1 - Collins, John A. A1 - Detrick, Robert S. A1 - Orcutt, John A. A1 - Bercovici, David A1 - Hauri, Erik H. KW - finite-frequency tomography KW - Hawaii KW - hotspot KW - mantle plume AB - Three-dimensional images of P-wave velocity structure beneath the Hawaiian Islands, obtained from a network of seafloor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated in the direction of the island chain and surrounded by a high-velocity anomaly in the shallow upper mantle that is parabolic in map view. Low velocities continue downward to the mantle transition zone between 410 and 660km depth and extend into the topmost lower mantle, although the resolution of lower mantle structure from this data set is limited. Comparisons of inversions with separate data sets at different frequencies suggest that contamination by water reverberations is not markedly biasing the P-wave imaging of mantle structure. Many aspects of the P-wave images are consistent with independent tomographic images of S-wave velocity in the region, but there are some differences in upper mantle structure between P-wave and S-wave velocities. Inversions without station terms show a southwestward shift in the location of lowest P-wave velocities in the uppermost mantle relative to the pattern for shear waves, and inversions with station terms show differences between P-wave and S-wave velocity heterogeneity in the shallow upper mantle beneath and immediately east of the island of Hawaii. Nonetheless, the combined data sets are in general agreement with the hypothesis that the Hawaiian hotspot is the result of an upwelling, high-temperature plume. The broad upper-mantle low-velocity region beneath the Hawaiian Islands may reflect the diverging “pancake” at the top of the upwelling zone; the surrounding region of high velocities could represent a downwelling curtain; and the low-velocity anomalies southeast of Hawaii in the transition zone and topmost lower mantle are consistent with predictions of plume tilt. VL - 303 UR - https://www.sciencedirect.com/science/article/pii/S0012821X11000161 ER - TY - JOUR T1 - Mantle Shear-Wave Velocity Structure Beneath the Hawaiian Hot Spot JF - Science Y1 - 2009 A1 - Wolfe, Cecily J. A1 - Solomon, Sean C. A1 - Laske, Gabi A1 - Collins, John A. A1 - Detrick, Robert S. A1 - Orcutt, John A. A1 - Bercovici, David A1 - Hauri, Erik H. AB - Defining the mantle structure that lies beneath hot spots is important for revealing their depth of origin. Three-dimensional images of shear-wave velocity beneath the Hawaiian Islands, obtained from a network of sea-floor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated in the direction of the island chain and surrounded by a parabola-shaped high-velocity anomaly. Low velocities continue downward to the mantle transition zone between 410 and 660 kilometers depth, a result that is in agreement with prior observations of transition-zone thinning. The inclusion of SKS observations extends the resolution downward to a depth of 1500 kilometers and reveals a several-hundred-kilometer-wide region of low velocities beneath and southeast of Hawaii. These images suggest that the Hawaiian hot spot is the result of an upwelling high-temperature plume from the lower mantle. VL - 326 UR - https://www.science.org/doi/full/10.1126/science.1180165 N1 - Publisher: American Association for the Advancement of Science ER -