High Magnitude

[Piperion Giles]

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Globally, the largest tsunamigenic earthquakes have occurred along subduction zones. Devastating events exceeding magnitude 9, such as those in Chile, Sumatra, and Japan, struck in regions lacking instrumental records of similar events. Despite the absence of such events along the 1000-kilometer-long Mexican subduction zone, historical and geologic evidence suggests the occurrence of a magnitude 8.6 tsunamigenic earthquake. However, the Guerrero seismic gap has not experienced a high-magnitude earthquake in over 100 years. Here we present results on analyses of sediment grain size, geochemistry, microfossils, magnetic properties, and radiometric and optical stimulated luminescence dating conducted along the Guerrero coast. We provide evidence of a 2000-year history of large tsunamis triggered by potentially large earthquakes. Numerical modeling supports our findings, indicating a magnitude >8 event around the year 1300 in the Guerrero seismic gap. This evidence underscores the importance of assessing earthquake and tsunami potential using long-term evidence and instrumental observations along subduction zones globally.

Our interpretation considers various factors influencing the observed changes in the depositional environment and microorganism habitat. While we acknowledge the possibility of secondary processes playing a role, our focus on the tsunami as the primary driver is supported by multiple lines of evidence, including sedimentology, diatom analysis, and topographical comparisons. We recognize the dynamic nature of coastal settings and the potential for natural processes to influence them, but the combination of evidence supports our interpretation of a tsunami-induced shift in the coastal environment.

We have examined a total of 38 sites, to address the question of a broad representation of evidence for land-level change, employing various methods such as cores, geoslices, pits, and hang-auger surveys to gather a comprehensive dataset. It is all included in Fig. 2a and Supplementary Table S1. Figure 2a and Supplementary Table S1 present the stratigraphy at each individual site, providing valuable insights into the sedimentary layers and changes observed. Furthermore, we have included information about the transition from intertidal to subtidal conditions, which can serve as a compelling indicator of land-level change. Please refer to Supplementary Fig. S3.

Furthermore, based on the information provided, ruptures along neighboring segments are unlikely to produce similar tsunami deposits or inundation patterns near site A1. The proximity to the coastline, as suggested by the coseismic deformation models in Supplementary Fig. S4, indicates a higher likelihood of coastal uplift rather than subsidence. Additionally, as shown in Supplementary Fig. S5b, even earthquakes with magnitudes greater than 8.3, such as in T9 scenario, do not generate amplitudes capable of inundating A1. Furthermore, historical evidence from earthquakes like Jalisco 1932 (Mw8.2), Michoacan 1985 (Mw8.1), and Oaxaca 1785 (M8.6) does not suggest the occurrence of subsidence or flooding capable of causing the observed tsunami deposits at A1 in the Guerrero Seismic Gap. Therefore, it is unlikely that ruptures along neighboring segments would produce similar effects in this specific location.

Recent geologic evidence provides new insights into extraordinary catastrophic events in the Mexican subduction zone. The occurrence of large events might be in the range of centuries. Our observations also indicate that indeed subduction zones might have variable rupture modes. The GSG and other segments on the MSZ and other subduction zones require combined long-term and instrumental observations to forewarn eventual catastrophes. Our findings offer evidence to prepare communities for earthquake and tsunami hazards.

We constructed stratigraphic cross sections using geoslices and pits (Fig. 2a). Focus was given to sites 9 sites, and at A1 and A2 for further sediment analysis, including grain size, diatoms, geochemistry, and different dating techniques37. Site A1 was used to study magnetic properties, including magnetic susceptibility and anisotropy of magnetic susceptibility (AMS).

Optical stimulated luminescence (OSL) analysis was performed at the Geoluminiscence Research Dating Lab facility at Baylor University. The collection of samples was performed as described by the facility ( =955930). Three samples were measured for OSL dates (Supplementary Table S4).

It is important to note that various dating methods often complement each other, contributing to a more robust chronological framework. In similar studies, multiple dating techniques have been successfully addressed different aspects of sedimentary sequences. Pb210 dating is suitable for younger sediments, OSL is effective for tsunami deposits, and C14 is utilized when organic matter is present. When combined, these methods enhance the reliability and accuracy of the chronological interpretation. Therefore, integrating multiple techniques is a well-established practice in sedimentary research using Pb210, C14, and OSL methods to date tsunami deposits42,43,44.

All information and data that are necessary to interpret, verify, and extend the research in the article are provided in the form of Supplementary Information. The data sets supporting tsunami modeling, sedimentology, and geochemical data presented in Fig. 3d and Supplementary Figs. S1, S2, S4, and S5, are publicly available on the Zenodo repository, as part of this record with the identifier:

M.T.R-H. conceived and carried out the research, data acquisition, lab analyses, and wrote the manuscript. N.C. carried out tsunami and earthquake modeling, created all final figures, and helped with the manuscript revision. J.C. performed diatom and AMS analysis and contributed with the related sections of an early version of this manuscript. K.G. drafted a figure, aided in data interpretation and manuscript revision. D.S. aided in initial subsampling, helped with data interpretation in the field. All authors mentioned above participated in the fieldwork. S.L.F. carried out OSL analysis. M.L.M-C. assisted with microfossil identification. A.G. assisted with AMS analysis. All authors revised the manuscript.

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Hippocampal CA3 neurons form synapses with CA1 neurons in two layers, stratum oriens (SO) and stratum radiatum (SR). Each layer develops unique synaptic properties but molecular mechanisms that mediate these differences are unknown. Here, we show that SO synapses normally have significantly more mushroom spines and higher-magnitude long-term potentiation (LTP) than SR synapses. Further, we discovered that these differences require the Type II classic cadherins, cadherins-6, -9, and -10. Though cadherins typically function via trans-cellular homophilic interactions, our results suggest presynaptic cadherin-9 binds postsynaptic cadherins-6 and -10 to regulate mushroom spine density and high-magnitude LTP in the SO layer. Loss of these cadherins has no effect on the lower-magnitude LTP typically observed in the SR layer, demonstrating that cadherins-6, -9, and -10 are gatekeepers for high-magnitude LTP. Thus, Type II cadherins may uniquely contribute to the specificity and strength of synaptic changes associated with learning and memory.

Innate immune responses rely on rapid and precise gene regulation mediated by accessibility of regulatory regions to transcription factors (TFs). In natural killer (NK) cells and other innate lymphoid cells, competent enhancers are primed during lineage acquisition, and formation of de novo enhancers characterizes the acquisition of innate memory in activated NK cells and macrophages. Here, we investigated how primed and de novo enhancers coordinate to facilitate high-magnitude gene induction during acute activation. Epigenomic and transcriptomic analyses of regions near highly induced genes (HIGs) in NK cells both in vitro and in a model of Toxoplasma gondii infection revealed de novo chromatin accessibility and enhancer remodeling controlled by signal-regulated TFs STATs. Acute NK cell activation redeployed the lineage-determining TF T-bet to de novo enhancers, independent of DNA-sequence-specific motif recognition. Thus, acute stimulation reshapes enhancer function through the combinatorial usage and repurposing of both lineage-determining and signal-regulated TFs to ensure an effective response.

Keywords: T-bet; Toxoplasma Gondii infection; de novo enhancers; innate lymphoid cells; lineage defining transcription factors; natural killer cells; poised enhancers; signal regulated transcription factors; signal transducer and activator of transcription (STAT) protein; super-enhancers.

The severity of an earthquake is generally proportional to the amount of seismic energy it releases. Seismologists use a Magnitude scale to express this energy release. Here are the typical effects of earthquakes in various magnitude ranges.

While each earthquake releases a unique amount of energy, the magnitude values reported by different seismological observatories for an event may vary. Depending on the size, nature, and location of an earthquake, seismologists may use several different methods and even different magnitude scales to estimate magnitude. The uncertainty in an estimate of the magnitude is about plus or minus 0.3 units, and seismologists often revise magnitude estimates as they obtain and analyze additional data. It may be several days before different organizations come to a consensus on what is the best overall magnitude estimate.

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