<i>P</i>-wave velocity structure of the uppermost mantle beneath Hawaii from traveltime tomography

Tilmann, Frederik; Benz, H.; Okubo, P.

doi:10.1046/j.1365-246x.2001.00480.x

Cited by 41 publications

(41 citation statements)

References 45 publications

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“…Conversely, Kilauea's conduit is in the zone of maximum bending that helps make it the most active deep earthquake zone under Hawaii. The lowest P wave velocity found by the teleseismic inversion of Tilmann et al [] at 35 km depth coincides with the aseismic hole that we interpret as the soft center of the broken plate. The deep earthquake rate under Kilauea dropped at the time of the M 7.2 south flank earthquake, as stress on the lithosphere was relieved by several meters of slip of the flank above. We thus infer that the rate of deep Kilauea earthquakes is caused by both loading and tractional stress from mobile flanks.…”

Section: Discussionsupporting

confidence: 80%

“…The P wave velocity structure from tomography reveals a low velocity structure [ Tilmann et al , , their Figures 4a and 4b] that coincides very well with the aseismic zone and stress center. The lowest velocity in their 35 km depth layer is under the summit region of Mauna Loa, and the slowness is about 5% compared to the NE and SW edges of the island.…”

Section: Discussionmentioning

confidence: 98%

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Lithospheric flexure under the Hawaiian volcanic load: Internal stresses and a broken plate revealed by earthquakes

Klein

2016

JGR Solid Earth

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Several lines of earthquake evidence indicate that the lithospheric plate is broken under the load of the island of Hawai`i, where the geometry of the lithosphere is circular with a central depression. The plate bends concave downward surrounding a stress‐free hole, rather than bending concave upward as with past assumptions. Earthquake focal mechanisms show that the center of load stress and the weak hole is between the summits of Mauna Loa and Mauna Kea where the load is greatest. The earthquake gap at 21 km depth coincides with the predicted neutral plane of flexure where horizontal stress changes sign. Focal mechanism P axes below the neutral plane display a striking radial pattern pointing to the stress center. Earthquakes above the neutral plane in the north part of the island have opposite stress patterns; T axes tend to be radial. The M6.2 Honomu and M6.7 Kiholo main shocks (both at 39 km depth) are below the neutral plane and show radial compression, and the M6.0 Kiholo aftershock above the neutral plane has tangential compression. Earthquakes deeper than 20 km define a donut of seismicity around the stress center where flexural bending is a maximum. The hole is interpreted as the soft center where the lithospheric plate is broken. Kilauea's deep conduit is seismically active because it is in the ring of maximum bending. A simplified two‐dimensional stress model for a bending slab with a load at one end yields stress orientations that agree with earthquake stress axes and radial P axes below the neutral plane. A previous inversion of deep Hawaiian focal mechanisms found a circular solution around the stress center that agrees with the model. For horizontal faults, the shear stress within the bending slab matches the slip in the deep Kilauea seismic zone and enhances outward slip of active flanks.

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Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 98%

Lithospheric flexure under the Hawaiian volcanic load: Internal stresses and a broken plate revealed by earthquakes

Klein

2016

JGR Solid Earth

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“…In this study relative arrival‐times determined in this way have mean standard deviation 0.02 s. In line with the studies of Bastow et al [2005] and Tilmann et al [2001]we regard the MCCC‐derived estimates of timing uncertainty as optimistic. Our final data set of relative arrival‐time residuals comprises ∼5100 earthquake–station pairs, whose distribution as a function of back azimuth and epicentral distance is shown inFigure 2.…”

Section: Methodssupporting

confidence: 65%

P‐wave tomography of eastern North America: Evidence for mantle evolution from Archean to Phanerozoic, and modification during subsequent hot spot tectonism

2012

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The unique physical and chemical properties of cratonic lithosphere are thought to be key to its long‐term survival and its resistance to pervasive modification by tectonic processes. Study of mantle structure in southeast Canada and the northeast US offers an excellent opportunity to address this issue because the region spans 3 billion years of Earth history, including Archean formation of the Superior craton and younger accretion of terranes to eastern Laurentia during the Proterozoic Grenville and Phanerozoic Appalachian orogenies. Trending NW–SE through each of these terranes is the track of the Great Meteor hot spot, which affected the region during the Mesozoic. Here we study mantle seismic velocity structure beneath this region of eastern North America using tomographic inversion of teleseismic P‐wave relative arrival‐times recorded by a large‐aperture seismograph network. There are no large‐scale systematic differences between Superior and Grenville mantle wave speed structure, which may suggest that tectonic stabilization of cratons occurred in a similar fashion during the Archean and Proterozoic. Cratonic lithosphere is largely thought to be resistant to modification by hot spot processes, in contrast to younger terranes where lithospheric erosion and significant magmatism are expected. Low velocities beneath the regions affected by the Great Meteor hot spot are broadest beneath the Paleozoic Appalachian terranes, indicating pervasive modification of the lithosphere during magmatism. The zone of modification narrows considerably into the Proterozoic Grenville province before disappearing completely in the Archean Superior craton, where the surface signature of Mesozoic magmatism is limited to kimberlite eruptions.

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“…In this study relative arrival times determined in this way have mean standard deviation 0.02 s, and 0.05 s for P and S waves, respectively. In line with the studies of Bastow et al [2005] and Tilmann et al [2001] we regard the MCCC derived estimates of timing uncertainty as optimistic.…”

Section: Methodsmentioning

confidence: 90%

Upper mantle seismic structure beneath the Ethiopian hot spot: Rifting at the edge of the African low‐velocity anomaly

Bastow

Nyblade

Stuart

et al. 2008

Geochem Geophys Geosyst

203

291

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[1] The Miocene-Recent East African Rift in Ethiopia subaerially exposes the transitional stage of rifting within a young continental flood basalt province. As such, it is an ideal study locale for continental breakup processes and hot spot tectonism. We combine teleseismic traveltime data from 108 seismic stations deployed during two spatially and temporally overlapping broadband networks to present detailed tomographic images of upper mantle P and S wave seismic velocity structure beneath Ethiopia. Tomographic images reveal a $500 km wide low P and S wave velocity zone at 75 to !400 km depth in the upper mantle that extends from close to the eastern edge of the Main Ethiopian Rift (MER) westward beneath the uplifted and flood basalt-capped NW Plateau. We interpret this broad low-velocity region (LVR) as the upper mantle continuation of the African Superplume. Within the broad LVR, zones of particularly low velocity are observed with absolute delay times (dt P $ 4 s) that indicate the mantle beneath this region is amongst the slowest worldwide. We interpret these low velocities as evidence for partial melt beneath the MER and adjacent NW Plateau. Surprisingly, the lowest-velocity region is not beneath Afar but beneath the central part of the study area at $9°N, 39°E. Whether this intense low-velocity zone is the result of focused mantle upwelling and/or enhanced decompressional melting at this latitude is unclear. The MER is located toward the eastern edge of the broad low-velocity structure, not above its center. This observation, along with strong correlations between low-velocity zones and lithospheric structures, suggests that preexisting structural trends and Miocene-to-Recent rift tectonics play an important role in melt migration at the base of the lithosphere in this magmatic rift zone.

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P-wave velocity structure of the uppermost mantle beneath Hawaii from traveltime tomography

Cited by 41 publications

References 45 publications

Lithospheric flexure under the Hawaiian volcanic load: Internal stresses and a broken plate revealed by earthquakes

Lithospheric flexure under the Hawaiian volcanic load: Internal stresses and a broken plate revealed by earthquakes

P‐wave tomography of eastern North America: Evidence for mantle evolution from Archean to Phanerozoic, and modification during subsequent hot spot tectonism

Upper mantle seismic structure beneath the Ethiopian hot spot: Rifting at the edge of the African low‐velocity anomaly

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