Validation of seismic hazard curves using a calibrated 14 ka lacustrine record in the Eastern Alps, Austria.

Seismic hazard maps are crucial for earthquake mitigation and mostly rely on probabilistic seismic hazard analysis (PSHA). However, the practise and value of PSHA are under debate because objective testing procedures for seismic hazard maps are scarce. We present a lacustrine turbidite record revealing 44 earthquakes over the last ~ 14 ka and use it to test seismic hazard curves in southern Austria. We derive local seismic intensities for paleo-earthquakes by applying scaling relationships between the sedimentary imprint and seismic intensity of well-documented historical earthquakes. The last ~ 2.8 ka of the record agree with a Poissonian recurrence behaviour and therefore a constant hazard rate, which is the modelling choice for standard PSHA. The lacustrine data are consistent with the intensity-frequency relationship of the local seismic hazard curve, confirming the current PSHA approach for this part of Austria. On longer timescales, distinct phases of enhanced regional seismicity occurred, indicating a potential increase of seismic hazard after large earthquakes-a factor hitherto disregarded in the PSHA of the Eastern Alps. Our new method forms an independent procedure to test hazard maps in any setting where suitable lake systems are available

Comparative single-cell genomics of Atribacterota JS1 in the Japan Trench hadal sedimentary biosphere

Deep-sea and subseafloor sedimentary environments host heterotrophic microbial communities that contribute to Earth’s carbon cycling. However, the potential metabolic functions of individual microorganisms and their biogeographical distributions in hadal ocean sediments remain largely unexplored. In this study, we conducted single-cell genome sequencing on sediment samples collected from six sites (7,445–8,023 m water depth) along an approximately 500 km transect of the Japan Trench during the International Ocean Discovery Program Expedition 386. A total of 1,886 single-cell amplified genomes (SAGs) were obtained, offering comprehensive genetic insights into sedimentary microbial communities in surface sediments (<1 m depth) above the sulfate-methane transition zone along the Japan Trench. Our genome data set included 269 SAGs from Atribacterota JS1, the predominant bacterial clade in these hadal environments. Phylogenetic analysis classified SAGs into nine distinct phylotypes, whereas metagenome-assembled genomes were categorized into only two phylotypes, advancing JS1 diversity coverage through a single cell-based approach. Comparative genomic analysis of JS1 lineages from different habitats revealed frequent detection of genes related to organic carbon utilization, such as extracellular enzymes like clostripain and α-amylase, and ABC transporters of oligopeptide from Japan Trench members. Furthermore, specific JS1 phylotypes exhibited a strong correlation with in situ methane concentrations and contained genes involved in glycine betaine metabolism. These findings suggest that the phylogenomically diverse and novel Atribacterota JS1 is widely distributed in Japan Trench sediment, playing crucial roles in carbon cycling within the hadal sedimentary biosphere

Linkage between Natural Disasters and Kiwulan Cultural Hiatus over the Last 1000 Years in the Lanyang Drainage System

台灣由於受到強烈的構造運動以及頻繁的颱風侵襲，不論是抬升速率、降雨量、剝蝕速率乃至於沉積速率皆十分快速而且獨特。颱風所帶來的強降雨使陸域河流系統中的山崩、洪水和土石流等自然災變屢見不鮮，不但造成自然環境的演變，也深深影響著這片土地上的人類活動。2009年的莫拉克風災即為一大型自然災變的現代類比，提供我們地質歷史中的災害線索。 淇武蘭遺址為蘭陽平原近年來發現的重要鐵器時代遺址，介於上、下文化層中間的文化空白，顯示此居住地曾經在西元1200-1500年左右被遺棄，到底是甚麼原因造成此文化空白實是一個有趣的問題。 本研究整合了蘭陽溪上游的階地定年、蘭陽平原上湖泊岩芯的有機物指標以及海洋岩芯的木屑豐度計數，重建過去千年來台灣東北部蘭陽溪流域系統的洪水事件。蘭陽溪上游分佈了一系列的沖積扇階地，反映了過去的土石流事件，整理其碳十四定年結果發現階地發育期集中在西元850-1100以及1400-1600年。而由蘭陽平原上大湖和梅花湖的總有機碳和碳氮比資料，以及由Itrax-XRF岩芯掃描儀所得到的梅花湖有機物指標、光學及X光攝像，顯示陸源物質在西元900-950以及1400-1500年這兩個時段大量進入湖泊沉積物中。位於和平海盆內的OR1-801-7A岩芯也在西元950-1050以及1450-1550年這兩個時段記錄到木屑豐度的極大值，與湖泊岩芯的陸源物質指示之洪水訊號近乎同時。 總而言之，由蘭陽溪流域系統的階地、湖芯和海洋岩芯所重建出的證據顯示，蘭陽溪流域系統在西元900-950以及1400-1500這兩個時期，洪水頻率和規模有顯著升高的狀況，使整個蘭陽溪流域系統從源到匯皆能記錄到洪水事件的斷簡殘篇。其中西元1400-1500年的洪水事件與淇武蘭遺址的文化空白近乎同時，本研究認為遺址的文化空白是因為受到洪水事件的影響，生活條件惡化使淇武蘭先民搬離原先的居住地。Active tectonic activities and frequent typhoon visits make Taiwan unique in having very high rates of uplift, precipitation, denudation and sedimentation. Particularly, intense rainfall associated with typhoons often causes natural disasters in river systems, such as flooding, large-scale landslides and debris flows, affecting human activities at the present time and in the past. Typhoon Morakot in 2009 may serve as a modern analog of such events in the geological past. Site Kiwulan is a newly discovered archaeological site of the Iron Age in Lan-Yang Plain. A cultural hiatus, found around 1200-1500 cal. yr AD, suggests that the settlement was once abandoned. It remains a mystery what caused this abandonment. This study assembles radiocarbon dates of upland river terraces, organic proxies in flood plain lake sediments and content of wood shreds in nearby marine sediment core. These records are synthesized to infer the frequency and magnitude of ancient floods over the past millennium in the Lan-Yang River system in northeastern Taiwan. Alluvial fan terraces distributed along the banks of upper Lan-Yang River are considered to be remains of ancient debris flow events, and their radiocarbon dates fall in two time ranges: 850-1100 and 1400-1600 cal. yr AD. Organic proxies such as TOC and C/N ratio representing terrestrial plant input were measured from bulk sediments of Lake Dahu and Lake Meihwa in the Lan-Yang Plain. Peak values of TOC, C/N ratio and organic indicator plus optical and radiographic images from ITRAX-XRF core scanner are conspicuous during 900-950, and 1400-1500 cal. yr AD, implying frequent flood events. Abundance peaks of wood shreds in marine box core ORI-801-7A occurred during 950-1050 and 1450-1550 cal. yr AD, coinciding with those terrestrial input events recorded in lake sediments. In summary, different lines of evidence collected from the Lan-Yang River system suggest that flood events were more frequent during two particular periods: 900-950 cal. yr AD and 1400-1500 cal. yr AD. The later period corresponds to the cultural hiatus at Site Kiwulan, suggesting that the lost civilization may be related to severe and frequent flooding of the Lan-Yang Plain during that period

Organic proxies and paleotemperature records of the central Sea of Okhotsk

The long-chain diol index (LDI) is a new organic sea surface temperature (SST) proxy based on the distribution of long-chain diols. It has been applied in several environments but not yet in subpolar regions. Here, we tested the LDI on surface sediments and a sediment core from the Sea of Okhotsk, which is the southernmost seasonal sea ice covered region in the Northern Hemisphere, and compared it with other organic temperature proxies, i.e. Uk'37 and TEXL86. In the surface sediments, the LDI is correlated with autumn sea surface temperature, similar to the Uk'37 but different from the TEXL86 that correlates best with summer sea subsurface temperature. Remarkably, the obtained local LDI calibration was significantly different from the global core-top calibration. We used the local LDI calibration to reconstruct past SST changes in the central Sea of Okhotsk. The LDI-SST record shows low glacial (Marine Isotope Stage, MIS 2, 4, 6) and high interglacial (MIS 1 and MIS 5) temperatures and follows the same pattern as the Uk'37-SST and a previously published TEXL86 temperature record. Similar to the modern situation, the reconstructed temperatures during the interglacials likely reflect different seasons, i.e. summer for the TEXL86 and autumn for Uk'37 and LDI. During glacials, the reconstructed temperatures of all three proxies are similar to each other, likely reflecting summer temperatures as this was the only season free of sea ice. Our results suggest that the LDI is a suitable proxy to reconstruct subpolar sea water temperatures

A Comparison of Late Quaternary Organic Proxy-Based Paleotemperature Records of the Central Sea of Okhotsk

The long-chain diol index (LDI) is a new organic sea surface temperature (SST) proxy based on the distribution of long-chain diols. It has been applied in several environments but not yet in subpolar regions. Here we tested the LDI on surface sediments and a sediment core from the Sea of Okhotsk, which is the southernmost seasonal sea ice-covered region in the Northern Hemisphere, and compared it with other organic temperature proxies, that is, Uk' 37 and TEXL 86. In the surface sediments, the LDI is correlated with autumn SST, similar to the Uk' 37 but different from the TEXL 86 that correlates best with summer sea subsurface temperature. Remarkably, the obtained local LDI calibration was significantly different from the global core-top calibration. We used the local LDI calibration to reconstruct past SST changes in the central Sea of Okhotsk. The LDI-SST record shows low glacial (Marine Isotope Stage, MIS 2, 4, and 6) and high interglacial (MIS 1 and MIS 5) temperatures and follows the same pattern as the Uk' 37-SST and a previously published TEXL 86 temperature record. Similar to the modern situation, the reconstructed temperatures during the interglacials likely reflect different seasons, that is, summer for the TEXL 86 and autumn for (Formula presented.) and LDI. During glacials, the reconstructed temperatures of all three proxies are similar to each other, likely reflecting summer temperatures as this was the only season free of sea ice. Our results suggest that the LDI is a suitable proxy to reconstruct subpolar seawater temperatures

Geological reference standards (JLK-1,JSD-1, JSD-2, JSD-3,JMS-1, JMS-2) measured by Itrax-XRF core scanner in different exposure times

X-ray fluorescence (XRF) core-scanning is a fast and nondestructive technique to assess elemental variations of unprocessed sediments. However, although the exposure time of XRF-scanning directly affects the scanning counts and total measurement time, only a few studies have considered the influence of exposure time during the scan. How to select an optimal exposure time to achieve reliable results and reduce the total measurement time is an important issue. To address this question, six geological reference materials from the Geological Survey of Japan (JLK-1, JMS-1, JMS-2, JSD-1, JSD-2, and JSD-3) were scanned by the Itrax-XRF core scanner using the Mo- and the Cr-tube with different exposure times to allow a comparison of scanning counts with absolute concentrations. The regression lines and correlation coefficients of elements that are generally used in paleoenvironmental studies were examined for the different exposure times and X-ray tubes. The results show that for those elements with relatively high concentrations or high detectability, the correlation coefficients are higher than 0.90 for all exposure times. In contrast, for the low detectability or low concentration elements, the correlation coefficients are relatively low, and improve little with increased exposure time. Therefore, we suggest that the influence of different exposure times is insignificant for the accuracy of the measurements. Thus, caution must be taken when interpreting the results of elements with low detectability, even when the exposure times are long and scanning counts are reasonably high

A Comparison of Late Quaternary Organic Proxy-Based Paleotemperature Records of the Central Sea of Okhotsk

The long-chain diol index (LDI) is a new organic sea surface temperature (SST) proxy based on the distribution of long-chain diols. It has been applied in several environments but not yet in subpolar regions. Here we tested the LDI on surface sediments and a sediment core from the Sea of Okhotsk, which is the southernmost seasonal sea ice-covered region in the Northern Hemisphere, and compared it with other organic temperature proxies, that is, Uk' 37 and TEXL 86. In the surface sediments, the LDI is correlated with autumn SST, similar to the Uk' 37 but different from the TEXL 86 that correlates best with summer sea subsurface temperature. Remarkably, the obtained local LDI calibration was significantly different from the global core-top calibration. We used the local LDI calibration to reconstruct past SST changes in the central Sea of Okhotsk. The LDI-SST record shows low glacial (Marine Isotope Stage, MIS 2, 4, and 6) and high interglacial (MIS 1 and MIS 5) temperatures and follows the same pattern as the Uk' 37-SST and a previously published TEXL 86 temperature record. Similar to the modern situation, the reconstructed temperatures during the interglacials likely reflect different seasons, that is, summer for the TEXL 86 and autumn for (Formula presented.) and LDI. During glacials, the reconstructed temperatures of all three proxies are similar to each other, likely reflecting summer temperatures as this was the only season free of sea ice. Our results suggest that the LDI is a suitable proxy to reconstruct subpolar seawater temperatures

Disentangling factors controlling earthquake-triggered soft-sediment deformation in lakes

In-situ soft sediment deformation structures (SSDS) are commonly used as paleoseismic indicators in marine and lacustrine sedimentary records. Earthquake-related shear can deform sediment in the shallow subsurface through Kelvin-Helmholtz instability. The SSDS related to Kelvin-Helmholtz instability have been used to quan-tify shaking strength of past earthquakes. However, the relative importance of i) lithology and physical proper-ties, ii) potential basal shear surfaces (e.g. clastic deposits), iii) slope angle, and iv) seismic shaking strength (e.g. peak ground acceleration) for deformation related to Kelvin-Helmholtz instability remains poorly studied. Lake Rinihue (south-central Chile) is chosen as a natural laboratory for disentangling the effect of the aforemen-tioned factors because i) the sediment composition of background sediment varies downcore and ii) volcanogenic clastic deposits are abundant within the sedimentary sequence. A previous study at lake Rinihue identified 25 SSDS intervals induced by historical earthquakes of varying rupture extent in 17 sediment cores taken at slope angles ranging from-0.2 degrees to-4.9 degrees (i.e. 16 slope sites and 1 basin site). Our study shows that defor-mation mostly occurs directly above volcanogenic deposits (i.e. 72 % of SSDS intervals), suggesting that volcanogenic deposits promote earthquake-induced deformation by strain softening, liquefaction or water film formation. Deformation thickness of SSDS increases with higher slope angles (i.e. strong positive correlation). Ad-ditionally, deformation thickness commonly corresponds to the stratigraphic depth of the youngest preceding volcanogenic deposit, but for steeper slope angles stratigraphically older volcanogenic deposits can function as basal shear surface. Therefore, we suggest that deformation thickness is primarily regulated by gravitational stress (i.e. slope angle) and secondarily by the stratigraphic depth of volcanogenic deposits. The earthquakes related to strongest shaking caused almost exclusively SSDS with highest deformation degrees (i.e. folds and intraclast breccia) as well as largest spatial extent of SSDS, resulting in highest numbers of related SSDS in the investigated cores. Thinner SSDS have higher deformation degrees at a given shaking strength, as seismically -induced shear energy acts more effectively on thinner deforming sequences. Therefore, we suggest that deforma-tion degree is primarily controlled by shaking strength and secondarily modulated by the thickness of the deforming sequences. We infer that deformation thickness is not a reliable indicator of paleoseismic shaking strength as this relies on many preconditioning factors independent of shaking strength. On the other hand, deformation degree can be a good proxy for shaking strength also in settings with varying lithotypes and intercalated clastic event deposits, provided multiple cores are studied to avoid under-or overestimation of paleoseismic shaking strength. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/)