Estimate of tsunami source using optimized unit sources and including dispersion effects during tsunami propagation: The 2012 Haida Gwaii earthquake

We apply a genetic algorithm (GA) to find the optimized unit sources using dispersive tsunami synthetics to estimate the tsunami source of the 2012 Haida Gwaii earthquake. The optimal number and distribution of unit sources gives the sea surface elevation similar to that from our previous slip distribution on a fault using tsunami data, but different from that using seismic data. The difference is possibly due to submarine mass failure in the source region. Dispersion effects during tsunami propagation reduce the maximum amplitudes by up to 20% of conventional linear long wave propagation model. Dispersion effects also increase tsunami travel time by approximately 1 min per 1,300 km on average. The dispersion effects on amplitudes depend on the azimuth from the tsunami source reflecting the directivity of tsunami source, while the effects on travel times depend only on the distance from the source.The sea bottom pressure data at the Ocean Bottom Seismograph stations used in this research were provided by instruments from the Ocean Bottom Seismograph Instrument Pool (http://www.obsip.org) which is funded by the US National Science Foundation. The facilities of the IRIS Data Management System were used to access the data used in this study. The sea level observations at the DART stations used in this research were provided by the National Oceanic and Atmospheric Administration and publicly available from http://nctr.pmel.noaa.gov/Dart/. The sea level observations at the tide gauge station in Canada were provided by the Canadian Hydrographic Service http://www.tides.gc.ca/eng. We thank Alexander Rabinovich (Institute of Ocean Sciences, Canada) for providing processed tide gauge data at the Canadian stations

Tsunami Data Assimilation Without a Dense Observation Network

The tsunami data assimilation method enables tsunami forecasting directly from observations, without the need of estimating tsunami sources. However, it requires a dense observation network to produce desirable results. Here we propose a modified method of tsunami data assimilation for regions with a sparse observation network. The method utilizes interpolated waveforms at virtual stations. The tsunami waveforms at the virtual stations between two existing observation stations are estimated by shifting arrival times with the linear interpolation of observed arrival times and by correcting the amplitudes for their water depths. In our new data assimilation approach, we employ the Optimal Interpolation algorithm to both the real observations and virtual stations, in order to construct a complete wavefront of tsunami propagation. The application to the 2004 Sumatra‐Andaman earthquake and the 2009 Dusky Sound, New Zealand, earthquake reveals that addition of virtual stations greatly helps improve the tsunami forecasting accuracy.GSGC Scholarship; KAKENHI. Grant Numbers: 16H01838, 15K1630

A 1000-yr-old tsunami in the Indian Ocean points to greater risk for East Africa

The December 2004 Sumatra-Andaman tsunami prompted an unprecedented research effort to find ancient precursors and quantify the recurrence time of such a deadly natural disaster. This effort, however, has focused primarily along the northern and eastern Indian Ocean coastlines, in proximal areas hardest hit by the tsunami. No studies have been made to quantify the recurrence of tsunamis along the coastlines of the western Indian Ocean, leading to an underestimation of the tsunami risk in East Africa. Here, we document a 1000-yr- old sand layer hosting archaeological remains of an ancient coastal Swahili settlement in Tanzania. The sedimentary facies, grain-size distribution, and faunal assemblages indicate a tsunami wave as the most likely cause for the deposition of this sand layer. The tsunami in Tanzania is coeval with analogous deposits discovered at eastern Indian Ocean coastal sites. Numerical simulations of tsunami wave propagation indicate a megathrust earthquake generated by a large rupture of the Sumatra-Andaman subduction zone as the likely tsunami source. Our findings provide evidence that teletsunamis represent a serious threat to coastal societies along the western Indian Ocean, with implications for future tsunami hazard and risk assessments in East Africa

Application of dense offshore tsunami observations from Ocean Bottom Pressure Gauges (OBPGs) for tsunami research and early warnings

We introduce a new data source of dense deep-ocean tsunami records 7 from Ocean Bottom Pressure Gauges (OBPGs) which are attached to Ocean Bottom 8 Seismometers (OBS) and apply them for far-field and near-field tsunami warnings. 9 Tsunami observations from OBPGs are new sources of deep-ocean tsunami 10 observations which, for the first time, provide dense tsunami data with spacing 11 intervals in the range of 10–50 km. Such dense data are of importance for tsunami 12 research and warnings and are capable of providing new insights into tsunami 13 characteristics. Here, we present a standard procedure for the processing of the 14 OBPG data and extraction of tsunami signals out of these high-frequency data. 15 Then, the procedure is applied to two tsunamis of 15 July 2009 Mw 7.8 Dusky 16 Sound (offshore New Zealand) and 28 October 2012 Mw 7.8 Haida Gwaii (offshore 17 Canada). We successfully extracted 30 and 57 OBPG data for the two aforesaid 18 tsunamis, respectively. Numerical modeling of tsunami was performed for both 19 tsunamis in order to compare the modeling results with observation and to use the 20 modeling results for the calibration of some of the OBPG data. We successfully 21 employed the OBPG data of the 2012 Haida Gwaii tsunami for tsunami forecast by 22 applying a data assimilation technique. Our results, including two case studies, 23 demonstrate the high potential of OBPG data for contribution to tsunami research 24 and warnings. The procedure developed in this study can be readily applied for the 2526 extraction of tsunami signals from OBPG data

Resveratrol increases rate of apoptosis caused by purine analogues in malignant lymphocytes of chronic lymphocytic leukemia

In this study, we attempted to assess the interactions of resveratrol, a natural compound present in various plant species, with the purine analogues fludarabine and cladribine in terms of their effects on DNA damage and apoptosis in chronic lymphocytic leukemia (CLL) cells. The experiments were performed ex vivo using short-term cell cultures of blood and bone marrow cells from newly diagnosed untreated patients. We analyzed the expression of active caspase-3 and the BCL-2/BAX ratio as markers of apoptosis and the expression of phosphorylated histone H2AX (γH2AX) and activated ATM kinase, which are reporters of DNA damage. The results of our study revealed that resveratrol induced apoptosis in CLL cells in a tumor-specific manner but did not affect non-leukemic cells, and apoptosis was associated with a decreased BCL2/BAX ratio. Here, we report for the first time that both resveratrol + fludarabine and resveratrol + cladribine caused a higher rate of apoptosis in comparison to the rate caused by a single drug. The percentage of apoptotic cells induced by resveratrol alone was higher in the group of patients with better prognostic markers than in those with worse prognostic markers. However, the rates of apoptosis caused by resveratrol combined with purine analogues were independent of ZAP-70 and CD38 expression and the clinical state of the disease; they were only dependent on the presence of high-risk cytogenetic abnormalities. We also observed an increase in γH2AX expression together with a rise in activated ATM in most of the analyzed samples. The obtained results indicate that resveratrol might warrant further study as a new therapeutic option for CLL patients. This naturally occurring substance may be used as a single agent, especially in older persons for whom there are some limitations for the use of aggressive treatment. On the other hand, a lower purine analogue dose could potentially be used in combination with resveratrol because of their combined effect. One of the mechanisms of action of resveratrol is the induction of DNA damage, which ultimately leads to apoptosis

Source modeling and spectral analysis of the Crete tsunami of 2nd May 2020 along the Hellenic Subduction Zone, offshore Greece

Tsunami hazard in the Eastern Mediterranean Basin (EMB) has attracted attention following three tsunamis in this basin since 2017 namely the July 2017 and October 2020 Turkey/Greece and the May 2020 offshore Crete Island (Greece) tsunamis. Unique behavior is seen from tsunamis in the EMB due to its comparatively small size and confined nature which causes several wave reflections and oscillations. Here, we studied the May 2020 event using sea level data and by applying spectral analysis, tsunami source inversion, and numerical modeling. The maximum tsunami zero-to-crest amplitudes were measured 15.2 cm and 6.5 cm at two near-field tide gauge stations installed in Ierapetra and Kasos ports (Greece), respectively. The dominant tsunami period band was 3.8–4.7 min. We developed a heterogeneous fault model having a maximum slip of 0.64 m and an average slip of 0.28 m. This model gives a seismic moment of 1.13 × 1019 Nm; equivalent to Mw 6.67. We observed three distinct wave trains on the wave record of the Ierapetra tide gauge: the first and the second wave trains carry waves with periods close to the source period of the tsunami, while the third train is made of a significantly-different period of 5–10 min.Royal Society, the United Kingdom

Tsunamis from the 29 March and 5 May 2015 Papua New Guinea earthquake doublet (M<inf>w</inf> 7.5) and tsunamigenic potential of the New Britain trench

© 2015. American Geophysical Union. All Rights Reserved.We characterized tsunamis from the 29 March and 5 May 2015 Kokopo, Papua New Guinea, Mw 7.5 earthquake doublet. Teleseismic body wave inversions using various rupture velocities (Vr) showed similar source-time functions and waveform agreements, but the spatial distributions of the slips were different. The rupture durations were ∼45 and ∼55s for the March and May events, with their peaks at ∼25 and at ∼17s, respectively. Tsunami simulations favored source models with Vr=1.75 and 1.50km/s for the March and May earthquakes. The largest slip on the fault was similar (2.1 and 1.7m), but the different depths and locations yielded maximum seafloor uplift of ∼0.4 and ∼0.2m. Tsunami simulation from hypothetical great earthquakes (M 8.4 and 8.5) on the New Britain trench showed that tsunami amplitudes may reach up to 10m in Rabaul, but most tsunami energy was confined within the Solomon Sea