Exploring Offshore Sediment Evidence of the 1755 CE Tsunami (Faro, Portugal): Implications for the Study of Outer Shelf Tsunami Deposits

Kümmerer, Vincent; Drago, Teresa; Veiga-Pires, C.; Silva, Pedro da; Magalhães, Vítor; Mena, Anxo; Lopes, Ana; Rodrigues, Ana Isabel; Schmidt, Sabine; Terrinha, Pedro; Baptista, Maria Ana

doi:10.3390/min10090731

Cited by 7 publications

(3 citation statements)

References 99 publications

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“…Thus, it is possible that the quartz grains analysed already held chemical imprints which supports the lack of microtextural heterogeneity in core GeoB23513-02. Di culties in recognising microtextural signatures related to tsunami events were reported in Kümmerer et al (2020), who investigated sediments from the 1755 CE tsunami on the southern Portuguese continental shelf, the in the vicinity of Faro. The authors detected only a small increase in percussion marks, and that a possible change in general sedimentation after the 1755 CE event may have in uenced the signature in the outer shelf sedimentary record.…”

Section: Microtextural Analysismentioning

confidence: 99%

Microtextural signatures in quartz grains and foraminifera from tsunami deposits of the Portuguese shelf

Yhasnara

Costa²,

Dourado³

et al. 2023

Geo-Mar Lett

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This study presents results from two sediment cores collected on the southern Portuguese shelf attempting to, partially, ll the knowledge gap of the offshore record of high-energy events. The results were obtained based on description of cores, microtextural analysis of quartz grains and foraminiferal taphonomy. The lithostratigraphy, corresponding to late Holocene sedimentation, with intercalations of medium sand-rich in bioclastic fragments with erosive basal contact. In terms of microtextures, a high degree of mechanical marks on the grains associated with tsunami deposition was observed and re ects the high-energy hydrodynamic processes. In compositional terms the higher presence of quartz grains in these units favours the increase of mechanical marks, because grain-to-grain contact is more intense.Additionally, the geomorphological setting of the coring sites determined the degree and type of mechanical microtextures observed. Furthermore, post-depositional changes and characteristics of the original sediment source contribute to explain the occurrence of dissolution in units of GeoB23513-02.The foraminiferal taphonomy displayed a predominance of dissolution alteration in the tests surfaces that was more evident in the silty layers. On the other hand, similarly to quartz grains microtextural signature, the sandy high-energy units exhibit a slight predominance of physical processes despite the still strong presence of dissolution. Furthermore, the sole presence of species (middle to outer shelf) in some units is an indication that there was little reworking of these specimens. Finally, the results obtained in this study show potential to recognize the microtextural signature of Holocene tsunami events in offshore environments.

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Section: Microtextural Analysismentioning

confidence: 99%

Microtextural signatures in quartz grains and foraminifera from tsunami deposits of the Portuguese shelf

Yhasnara

Costa²,

Dourado³

et al. 2023

Geo-Mar Lett

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“…Nevertheless, there have been a few studies dealing with backwash deposits associated with the 2004 tsunami (e.g., Sakuna et al, 2012;Sakuna-Schwartz et al, 2015), while the 2011 event led to an increased number of studies of offshore deposits and related processes (e.g., Ikehara et al, 2014Ikehara et al, , 2016Ikehara et al, , 2020Ikehara et al, , 2021Tamura et al, 2015;Yoshikawa et al, 2015;Seike et al, 2016). Recent investigations have also been made of backwash deposits associated with historical and prehistorical events (e.g., Kümmerer et al, 2020;Smedile et al, 2020;Feist et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

Offshore evidence of historic and prehistoric tsunamis on the north shore of Tutuila (American Samoa)

Riou,

Chaumillon,

Chagué

et al. 2024

Sedimentary Geology

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“…Studies that date successive sequences of extensive tsunami sand sheets in Alaska, Chile, Japan, Russia and New Zealand have contributed important understanding of the location of frequency of subduction zone ruptures (Ando et al, 2018;Ely et al, 2014;Hutchinson & Clague, 2017;Ishimura, 2017;León et al, 2022;Pinegina & Bourgeois, 2001;Pizer et al, 2021). Driven by the 2011 Tōhoku-oki earthquake (Tamura et al, 2015;Yoshikawa et al, 2015) some studies have also considered the value of tsunami deposits preserved in shallow offshore regions as recorders of past earthquakes but these has been less widely applied thus far (Costa et al, 2021;Feist et al, 2023;Kümmerer et al, 2020;Quintela et al, 2016;Riou et al, 2020).…”

Section: Paleotsunami Depositsmentioning

confidence: 99%

Integrating onshore and offshore paleoseismic evidence to reveal past large earthquakes on the weakly coupled central Hikurangi margin, New Zealand

Pizer

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Determining the location and recurrence of seismic slip at subduction zones is essential for constraining the hazard posed by great earthquakes. Although modern geodetic observations have revealed interseismically locked regions of the plate interface, it is unclear to what degree this reflects the potential for future rupture given the broad spectrum of possible slip behaviour and short instrumental record. Developing paleoearthquake records over multiple seismic cycles is therefore a powerful method of understanding spatiotemporal patterns in seismic slip behaviour at subduction margins. Conditionally stable parts of the plate interface adjacent to locked patches are identified as particularly important places to constrain long-term behaviour due to their potential to host multiple styles of interface slip.This thesis explores temporal variation in slip behaviour at subduction zones by investigating the paleoseismic record on the weakly coupled central Hikurangi margin in New Zealand. Previously, interpretation of paleoearthquake evidence in this region has been hindered by poorly constrained chronology, sparse distribution of study sites and incomplete consideration of source faults. Generating new paleoearthquake records was therefore necessary to constrain the timing and extent of large earthquakes, and to decipher whether they could represent rupture of the plate interface. Where precisely-dated tephra isochrons are available, they can provide a useful tool for accurate chronostratigraphic correlation between paleoseismic sites and improved temporal constraints within age-depth models of Holocene paleoearthquake chronologies. The age of the Waimihia tephra isochron was refined to 3574–3478 cal yr BP using integrated age modelling of 42 radiocarbon dates from proximal, distal onshore, and distal offshore locations. Using the refined isochron age alongside 68 radiocarbon dates, a new 5000-year record of four precisely-dated paleoearthquakes was generated at the Pakuratahi Valley near Napier, as a key locality for examining onshore coseismic deformation on the central Hikurangi margin. The evidence of both coseismic subsidence and uplift could have been caused by earthquakes on upper plate faults and/or the plate interface. To better distinguish between these sources and expand the paleoseismic record in space and time, a 7000- year record of seismoturbidites was developed from a suite of submarine sediment cores spanning the central margin. Integrating the onshore and offshore datasets permitted better characterization of evidence for widespread synchronous deformation across the central margin. The new interpretation of paleoseismic correlations suggests rupture of upper plate faults could generate some of the observed patterns of surface deformation, but that seismic slip on the subduction interface is likely for most earthquakes.Temporal agreement between the central Hikurangi paleoearthquakes and subduction earthquakes recorded on the southern, locked section of the margin provides strong evidence that multi-section ruptures, spanning a distance of >300 km, may have occurred. Examining the pattern of coseismic deformation on the central margin alongside current understanding of geophysical properties highlights the weakly coupled region of the interface between slow slip zones as an important location for propagating rupture along-strike from the locked patch. Conditional stability of this region is implied as a mechanism for supporting coseismic slip on the currently creeping part of the central Hikurangi margin. These observations add to the growing literature that suggests weakly coupled parts of the plate interface adjacent to locked patches can host multiple modes of interface slip and should therefore be considered a region of significant seismic hazard, due to their ability to support great (>Mw 8) multi-section subduction earthquakes.

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Exploring Offshore Sediment Evidence of the 1755 CE Tsunami (Faro, Portugal): Implications for the Study of Outer Shelf Tsunami Deposits

Cited by 7 publications

References 99 publications

Microtextural signatures in quartz grains and foraminifera from tsunami deposits of the Portuguese shelf

Microtextural signatures in quartz grains and foraminifera from tsunami deposits of the Portuguese shelf

Offshore evidence of historic and prehistoric tsunamis on the north shore of Tutuila (American Samoa)

Integrating onshore and offshore paleoseismic evidence to reveal past large earthquakes on the weakly coupled central Hikurangi margin, New Zealand

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