The energetic 2010 MW 7.1 Solomon Islands tsunami earthquake (original) (raw)
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Earthquake multiplets in the southeastern Solomon Islands
Physics of the Earth and Planetary Interiors, 1986
Analyses of P-wave first-motions, aftershock distributions, P-waveforms recorded at epicentral distances of 30°to 90°on the WWSSN, and 256 s-period Rayleigh-wave spectra obtained from the IDA and GDSN networks are used to examine the source characteristics of the events. The close temporal association and large size of earthquakes precluded collection of useful seismograms for the latter of the two 1966 events and the second and third events of the 1977 sequence. P-waveforms analyzed show smooth traces that can be modeled with simple trapezoidal source-time functions located at shallow (15-45 km) depths. Focal mechanisms are consistent with oblique subduction of the Indian plate beneath the Pacific plate at about N73°E.Estimates of seismic moment for individual events range from 0.2 to 2.3 X 1027 dyne-cm. Average stress drops of the sequences are estimated to range between 10 and 40 bars. This section of island arc may have ruptured in a similar sequence of earthquakes during the 1930's. Conversion of the cumulative seismic moment to displacement and averaging over 40 years suggests a convergence rate of about 4.5 cm year~, about one half of the rates that have been assessed on the basis of seafloor magnetic lineations.
Science of Tsunami Hazards, 2020
The present study examines the crustal deformational characteristics caused by earthquakes occurring primarily on the outer-rise of the oceanic lithosphere in zones of tectonic plate collision and subduction. Additionally it examines the possible reasons why more significant and catastrophic tsunamis are generated in such regions. The analysis is based primarily on observations of the extreme tsunami in the Samoan Islands region, which was generated by the large magnitude earthquake of 29 September 2009, which had its epicenter and tsunami generating area on the front end of the outer-rise of the seismically active northern end of the Tonga Trench and Arc. This is a region where there is greater obliquity of collision, substantial crustal deformation of the ocean floor, and a sharp change in direction of the zone of subduction towards the West. Also, this zone is characterized by extraordinary seismic activity of the oceanic slab, which subducts into the earth's mantle at the hi...
Geophysical Journal International, 2003
The Solomon Islands arc area is a complex plate convergence zone. At the North Solomon Trench on the northern side of the arc, it is believed that the Pacific Plate was subducting before coming into collision with the Ontong Java Plateau, the world's largest oceanic plateau. After the collision about 5 Ma, northeastward subduction initiated along the southern side of the arc at the San Cristobal Trench, another trench on the south side. GPS observations and crustal seismic structure surveys confirm that convergence occurs at both trenches. Without detailed and accurate seismicity, it is difficult to characterize the plate subduction to reveal the tectonics of such a complex zone where a key mechanism of continental growth may also exist. In 1994, an ocean-bottom seismometer (OBS) experiment was carried out for the first time in the area around the Solomon Islands arc to locate microearthquakes. Observations started in late August and continued until early September. Five digital recording OBSs were deployed around the Russell Islands west of Guadalcanal Island. OBS spacing was about 20 km. All the OBSs were recovered and yielded data with a good signal-to-noise ratio. 40 earthquakes, with magnitudes in the range 1.5-4.4 were located over 8 days. The seismicity clearly images the two subducting plates. Though the seismicity beneath the arc side slope of the San Cristobal Trench is relatively high, we can see the seismicity which is related to the subducting Pacific Plate beneath Santa Isabel Island. In addition, earthquakes occur within the crust beneath the southern part of the New Georgia Basin and the Russell Islands. An aseismic area extending 40 km inward from the San Cristobal trench axis implies initial aseismic slip of the India-Australia Plate at a small dip angle.
Tsunami as agents of geomorphic change in mid-ocean reef islands
Geomorphology, 2008
Low-lying atoll islands appear highly vulnerable to the effects of climate change and extreme natural events. Potentially disastrous effects of future sea-level rise have been inferred in many studies, and the actual impacts of tropical storms on island destruction and formation have been well documented. In contrast, the role of tsunami in the geomorphic development of atoll islands has not been investigated. The Sumatran earthquake of 26 December 2004 generated a tsunami that reached the Maldives 2500 km away, with waves up to 2.5 m high. Observations on the geomorphic changes resulting from the tsunami are detailed here, based on pre-and posttsunami profile measurements of island, beach and reef topography, and GPS surveys of the planform shape of islands and beaches of 11 uninhabited islands in South Maalhosmadulu atoll, Maldives. Erosional and depositional impacts were observed on all islands and these have been quantified. In general the changes were of a minor nature with a maximum reduction in island area of 9% and average of 3.75%. Rather, the tsunami accentuated predictable seasonal oscillations in shoreline change, including localised erosion reflected in fresh scarps and seepage gullies. Depositional features in the form of sand sheets and sand lobes emplaced on the vegetated island surfaces provide clear evidence that the tsunami waves washed over parts of all the islands. Both erosional scarps and overwash deposits were concentrated at the tsunami-exposed eastern sides of the islands. Impacts on leeward shores were primarily accretionary, in the form of spit and cuspate foreland extension. Whereas the nature and magnitude of intra-and inter-island impacts was variable, an east to west decline in aggregate effects was noted. Detailed consideration of the morphodynamic interaction between the tsunami waves and island morphology, show that this cross-atoll gradient resulted not just from the reduction in tsunami energy as it passed through the atoll, but also from variations in elevation of the encircling island ridge, and the quantity and distribution of sediment in the antecedent beach. A conceptual model identifying the sequence of changes to individual islands supports the observational data and the pattern of geomorphic changes resulting from the tsunami. This model leads to consideration of the longer-term impacts of the tsunami on the future stability of islands. Four scenarios are presented, each of which has a different island-beach sediment budget, and different relaxation time to achieve dynamic equilibrium.
A Near-Vertical Slab Tear in the Southeastern Solomon Islands
The Solomon Islands is one of the most seismically active areas in the southern Pacific with high earthquake hazard potential. The regional seismic network, equipped with six broadband seismic stations, was constructed as late as October 2018. On January 27 and 29, 2020, two moderate earthquakes, Mw 6.3 and 6.0, respectively, occurred in the southeastern Solomon Islands. The entire foreshock-main-shock-aftershock sequence was recorded by this seismic network for exploring the seismogenic structures. Based on the spacial distribution of the foreshock-aftershock sequence, the interaction of the subduction and transform zones between the Pacific and the Australia plates could lead to the near-vertical dip-slip tear slab. Confirmed with PREM and the new 1D velocity model for testing the robustness of the earthquake locations, a seismic gap at depths from 25 to 35 km is observed as the “jelly sandwich” rheology of the continental crust of the Australia plate.
Western Caribbean North American–Caribbean plate margin Roatan Island Uplifted and warped coastal landforms (fossil coral reef and beachrock, wave-cut and beach terraces) on the western part of Roatan Island off the northern Honduran coast record at least two late Holocene earthquakes that we estimate to have had magnitudes of N M7. Uplift has been primarily related to a fault that follows the southern coast of western Roatan, herein termed the " Flowers Bay fault " , a subsidiary fault of the Motagua/ Swan Islands Fault System which marks the boundary between the North American and Caribbean plates. Using electron spin resonance (ESR) and radiocarbon ages of calcium carbonate samples and a late Quaternary sea level elevation curve that is compatible with Caribbean sea level data, we constrain the ages and long-term uplift rates of the displaced landforms on Roatan caused by the vertical component of slip on the Flowers Bay fault. The fossil reef that is uplifted along the fault grew between 43 and 34 ka, and the beachrock horizon and lowest uplifted terrace along the southern and western coasts developed between 1000 and 1700 AD. We describe evidence of one earthquake that raised the south coast ~3 m (as much as 5 m locally) and that postdates 1700 AD. We interpret this event to be the great earthquake of August 1856 that generated a tsunami which ran as much as 24 km onto the mainland. Another earthquake circa 900 AD produced a similar amount of uplift as the 1856 event and likely generated a similar tsunami. The age and elevation of the fossil reef suggest a long-term uplift rate of 3 mm/year, consistent with a recurrence interval of ~ 1000 years for these large earthquakes.
Journal of Geophysical Research: Solid Earth, 2003
This paper presents a combined analysis of data collected both onshore and offshore in the epicentral region of the Mw 7.5, 26 November 1999, Ambrym earthquake. This offshore event occurred at the southern end of the back‐arc thrust belt of the Vanuatu subduction zone, east of the island of Ambrym and resulted in permanent uplift of the eastern tip of the island. The data presented include (1) interpretation of older seismic lines across the tectonic front, (2) compilation of aftershock sequences, (3) postseismic bathymetry from multibeam surveys, (4) measurements of permanent coseismic ground motion using desiccated red algae, uplifted beaches, and uplifted coral colonies, and (5) dating of raised corals exposed along the coastal cliff. The active scarp of the main fault appears 13 km east of the eastern tip of Ambrym (40 km long, 2 km depth, 950 m maximum step). Uplift rates of 3.5–4 mm/yr for the past 8000 years are calculated by dating raised corals. This leads to a longer seism...