Tsunami Period Research Articles

The 2020 Mw 7.0 Samos (Eastern Aegean Sea) Earthquake: joint source inversion of multitype data, and tsunami modelling

SUMMARY We present a kinematic slip model and a simulation of the ensuing tsunami for the 2020 Mw 7.0 Néon Karlovásion (Samos, Eastern Aegean Sea) earthquake, generated from a joint inversion of high-rate GNSS, strong ground motion and InSAR data. From the inversion, we find that the source time function has a total duration of ∼20 s with three peaks at ∼4, 7.5 and 15 s corresponding to the development of three asperities. Most of the slip occurs at the west of the hypocentre and ends at the northwest downdip edge. The peak slip is ∼3.3 m, and the inverted rake angles indicate predominantly normal faulting motion. Compared with previous studies, these slip patterns have essentially similar asperity location, rupture dimension and anticorrelation with aftershocks. Consistent with our study, most published papers show the source duration of ∼20 s with three episodes of increased moment releases. For the ensuing tsunami, the eight available gauge records indicate that the tsunami waves last ∼18–30 hr depending on location, and the response period of tsunami is ∼10–35 min. The initial waves in the observed records and synthetic simulations show good agreement, which indirectly validates the performance of the inverted slip model. However, the synthetic waveforms struggle to generate long-duration tsunami behaviour in simulations. Our tests suggest that the resolution of the bathymetry may be a potential factor affecting the simulated tsunami duration and amplitude. It should be noted that the maximum wave height in the records may occur after the decay of synthetic wave amplitudes. This implies that the inability to model long-duration tsunamis could result in underestimation in future tsunami hazard assessments.

Estimating the eruption-induced water displacement source of the 15 January 2022 Tonga volcanic tsunami from tsunami spectra and numerical modelling

The 15 January 2022 Tonga volcanic tsunami was a unique event as it was the only event after the 1883 Krakatau volcanic tsunami that created waves by a dual-mechanism generation process comprising atmospheric pressure waves and eruption-induced water displacements. Here, we study 22 tide gauge waveforms, eight DART (Deep-ocean Assessment and Reporting of Tsunamis) records, eight air pressure time series, apply spectral analysis, and conduct numerical modelling to develop a source model. Our source model accounts only for the contribution of eruption-induced water displacement. The maximum overall coastal tide gauge amplitudes were in the range of 4.2–148.8 cm, whereas DARTs registered maximum amplitudes of 3.6–21.4 cm. We identified the dominant tsunami periods due to the localized water displacement mechanism as 10–17 min and 4–7 min. The waves generated by atmospheric pressure waves had a period of 7–10 min and an amplitude of 9–19 cm on coastal tide gauges; the corresponding values for DARTs were 30–60 min and 4.2–15.7 cm. Modelling showed that the eruption-induced water displacement source had a characteristic initial length of 12 km, a maximum initial amplitude of 90 m, and a volume of 6.60 × 109 m3.

An approach for quantifying nearshore tsunami height probability and its application to the Pearl River Estuary

This study focuses on the coast around the Pearl River Estuary, and assesses tsunami hazard posed by the earthquakes along the Manila Trench. A probabilistic tsunami hazard assessment (PTHA) has been conducted based on 1,380,000 potential earthquake scenarios, in order to consider the uncertainty of seismic parameters as much as possible. To achieve such a large number of scenario simulations, the tsunami at an offshore position is firstly simulated based on a superposition approach proposed in previous studies, and then the joint probability density of incident tsunami period and height at the offshore position is obtained. After that, an amplification factor is adopted to estimate nearshore tsunami height probability from the offshore position. The amplification factor is the main concern in this study. It is commonly estimated from the Green’ law based on the linear wave shoaling theory, which is a simple and effective way. However, it may loss accuracy in the coast with complicate topography and tortuous shoreline. This study numerically obtained a dataset of wave amplification factors along the concerned coast, using the two-dimensional FUNWAVE-TVD model based on the Boussinesq equations. The results confirm the significance of incident wave period and height on the amplification factor, and suggest a more carefully estimation on the amplification factor should be taken into consideration. Based the newly obtained dataset of wave amplification factors, the quantified tsunami hazard probability along the concerned coast is given.

Analisis Ekspor Karet Provinsi Jambi ke India pada Periode Tsunami Covid-19

The economy of Jambi Province is supported by the agricultural sector with a contribution to the Gross Regional Domestic Product (GRDP) reaching 30.85 percent. The most dominant sub-sector is an annual plantation with palm oil and rubber as the main commodities. Nationally, the rubber plantation area of Jambi Province is in third place after the provinces of South Sumatra and North Sumatra. Rubber is a source of livelihood for the people of Jambi and a source of foreign exchange because rubber is the prima donna of Jambi Province exports. One of the rubber export destinations for Jambi Province in India. The Covid-19 tsunami that hit India in March-June 2021 is expected to affect Jambi Province's rubber exports. An analysis will be carried out on the development of Jambi Province's rubber exports during the Covid-19 tsunami period and see the effect of the Covid-19 tsunami in India on Jambi Province's rubber exports. This study uses descriptive analysis, normality test, and independent sample t-test to see the effect of the Covid-19 tsunami on rubber exports to India. The results of the Kolmogorov Smirnov normality test reached a significance of 0.200. Meanwhile, the normality test with Shapiro Wilk stated a significance of 0.720 before the Covid-19 tsunami and 0.161 during the Covid-19 tsunami. This means that Jambi Province's export data is normal because the significance is > 0.05. The results of the independent sample T-test on export data show that the Covid-19 tsunami did not affect Jambi Province's export activities to India. This can be observed from the significance value at equal variances assumed of 0.482 (> 0.05). This means that rubber exports to India will continue despite extraordinary events such as the COVID-19 tsunami.

Relation between the period of leading tsunami wave and source parameters

Tsunami waves can be significantly amplified by coastal topography, and it is known that the amplification is greatly associated with the period of tsunami wave. This study focuses on the period of leading tsunami wave and aims to find out its relationship with the source parameters. Statistics on the water level records of historical tsunami events show that the leading wave in most events is risky and its period has significant correlation with some source parameters. To clarify the relationship between the leading wave period and the source parameters, an analysis based on the numerical simulation of idealized tsunami scenarios has been conducted. The results suggest that the leading wave period shows strong anisotropy associated with the feature of seismic source. The period in the major direction is mainly affected by the magnitude and focal depth. In addition, water depth near the source also shows a great influence to the period in the idealized cases, but the influence is concealed by the complex topography in the real situation. Based on the idealized analysis, a formula for estimating the period of tsunami leading wave is proposed and applied to historical events. Reasonable predictions are obtained for tsunamis originated from deep water.

Effects of Depth of Fault Slip and Continental Shelf Geometry on the Generation of Anomalously Long‐Period Tsunami by the July 2020 Mw 7.8 Shumagin (Alaska) Earthquake

AbstractThe July 2020 Mw 7.8 Shumagin earthquake occurred in the seismic gap region along the Aleutian subduction zone. This interplate earthquake generated a small tsunami, but with unusual long‐period waves ranging between 40 and 90 min. We examined the cause of such an anomalous ocean wave through a source modeling inverted from tsunami and geodetic data. Our model indicates that the plate‐boundary rupture area was confined at depths of 20–40 km, although the slip resolvability decreases with depth. The coseismic seafloor displacement predominantly took place on the shallow continental shelf. Therefore, the initial water surface displacement at a mean water depth of ∼200 m is responsible for the long‐period waves, because tsunami period is inversely proportional to the square root of water depth. Furthermore, tsunami modeling implies that slip shallower than 20 km depth in the Aleutians would displace the seafloor beyond the continental shelf and generate shorter tsunami periods.

Indonesia paleotsunami database as an effort to reduce the tsunami disasters in Indonesia

Indonesia’s tectonic activity is one of the most active in the world. These conditions make Indonesia prone to earthquakes, tsunamis, and volcanic eruptions. Tsunamis are large ocean waves that are formed through several processes such as underwater earthquakes, underwater landslides, volcanic activity, and asteroid impacts. Indonesia has been hit by various tsunami events. However, not all characteristic tsunami events are well known and recorded. Knowing the characteristics of a tsunami occurrence is very important to understand the frequency and intensity of tsunamis in the present. This research create a WebGIS database for paleotsunami in Indonesia. Tsunami incident data comes from literature related to tsunami events such as books, journals, reports, final projects, and others. Making WebGIS in this study will be developed using website programming, namely HTML, CSS, and JavaScript. The research results obtained 302 tsunami data. The period of tsunami in this research is from Late Miocene to the last tsunami in 2018. The WebGIS created presents a database of tsunami events in Indonesia, a dashboard of Indonesian tsunami statistics, and a tsunami learning educational feature. It is hoped that the results of this database will serve as a means of information for future paleotsunami research needs and as a means of education regarding the potential for tsunamis in Indonesia.

CFD investigations of tsunami-induced scour around bridge piers

Tsunamis impacting on the coastal bridges could cause severe scour around piers, which subsequently threatens the stability of bridge foundations. This paper presents a numerical investigation on tsunami-induced scour around bridge piers based on a CFD model coupling hydrodynamic, sediment transport, and morphological models. The tsunami generation is numerically realized by prescribing a time-varying soliton flow in the inlet boundary. The model is first validated by comparing with available experimental results, which shows that it can accurately simulate the tsunami-induced velocity field, as well as the time development of the scour and the final scour depth. Based on the reliable CFD model, a total of 14 numerical experiments of tsunami-induced pier scour are then performed. The temporal development of scour indicates that substantial scour is occurred during the 0.4 to 0.6 times of the tsunami period. The scour rate highly depends on the tsunami period T and peak velocity Um, and the scour rate is enhanced significantly with the increase of either T or Um. The relative scour depth (normalized by the final scour depth) S/Sf over normalized time t/T for all the cases are generally collapsed to one curve that can be represented by a tanh function, and a simple equation is proposed to predict the final scour depth. Finally, a practical engineering methodology is established to predict the tsunami-induced pier scour, including the temporal scour development and the final scour depth. It demonstrates that this method is capable of reasonably predicting all the cases considered in this study.

Numerical Investigation of the Effectiveness of Vegetation-Embankment Hybrid Structures for Tsunami Mitigation Introduced after the 2011 Tsunami

As a mitigation measure against a tsunami inundation, vegetation-embankment hybrid structures received attention after the 2011 Great East Japan Tsunami, and some structures have already been constructed or are under construction in Japan. The present study conducted a series of numerical simulations using a hybrid system comprised of an artificial structure (an embankment, moat) and a natural component (vegetation) that was experimentally proposed in previous studies as an effective structure for tsunami mitigation. After validating the numerical model using published data, this study investigated differences in the performance of the hybrid system by changing the tsunami period and height characteristics of the tsunami-like surge-type flow. As a result, the delay in tsunami arrival time (ΔT) was not affected by the tsunami wave period for the investigated hybrid structures. Among the investigated structures, Case Ve40ME (where Ve40, M, and E represent vegetation, moat, and embankment, respectively, in that order from seaward) showed the maximum performance of ΔT. The reductions of overflow volume (ΔQ), fluid force index (RFI), and moment index (RMI) declined during the tsunami period. The tsunami mitigation effect is closely related to the relationship between the development times of backwater rise, hydraulic jump, and the tsunami period. Case Ve40ME was effective for ΔT, ΔQ, and RMI. Case EMVe40 was especially effective for RFI. When the tsunami period is short, the water level at the shoreline starts to decrease before full development of the hydraulic jump generated in the hybrid system. Thus, overflow volume to landward decreases, and the mitigation effects increase. When the tsunami period is long, the receding phenomenon at the peak water level does not affect the maximum values, thus the mitigation effects become smaller compared with the short period. However, the superiority to other structures is maintained in Case Ve40ME and Case EMVe40 with seaward vegetation and landward vegetation, respectively.

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.

POST TSUNAMI IMPACT ON HYPERTENSION AND DIABETES MELLITUS CASES IN PANDEGLANG DISTRICT, BANTEN, INDONESIA

Background: Pandeglang, a district in Banten province, Indonesia, was the worst affected area of the Sunda Strait tsunami which occurred on 22nd December, 2018. Aside from threats of communicable disease outbreaks, the district faced the challenges of managing non-communicable diseases (NCD) in the community. Purpose: The aim of the study is to describe the post tsunami impact on cases of hypertension and diabetes mellitus and the expected one-year projections of these diseases in the district of Pandeglang, Banten. Methods: In January 2019, we collected primary data from Pandeglang District Health Office (DHO) and 15 Public Health Centres (PHCs) that were heavily affected by the tsunami. Surveillance officers were also interviewed for their subjective opinions on disease projections in both the DHO and PHCs. Aggregated data of cases presenting to the PHCs for assistance were analysed in relation to the post tsunami period. The diseases of interest included hypertension and diabetes mellitus. Results: Reported cases of hypertension and diabetes mellitus increased a few days after the tsunami. For hypertension, the cases spiked on the 5th and 8th days, but for diabetes mellitus the spike came much later. Average cases of hypertension and diabetes mellitus per PHC were 62 and 3, respectively. At district and PHC level, hypertension and diabetes mellitus were considered as minor contributing factors to the morbidity and mortality in the affected communities. The projection of these diseases was optimistic after the first month. Conclusion: It can be concluded that the volume of cases with hypertension and diabetes in the district of Pandeglang tended to be in the first few weeks post tsunami These diseases are projected to lessen in the second month after the disaster due to the recovery of local health services.

Seiсhes Excited by the Atmospheric Disturbances within the Range of the Meteotsunami Periods nearby the Southern Part of the Sakhalin Island

Purpose. The aim of the paper is to study four synoptic situations, in which the seiches energy increase was observed in the coastal zone of the southern part of the Sakhalin Island, and to consider their possible meteorological origin. Methods and Results. Records of the waves obtained in the Institute of Marine Geology and Geophysics in 2008 using both the instruments installed in eight points in the coastal zone of the southern part of the Sakhalin Island, and the synoptic maps provided by the Sakhalin Hydrometeorological Service Department, were used. For all the observation points, four synoptic situations characterized by increase of the seiches energy within the meteotsunami existence range were considered. It is shown that the amplitudes of the main part of the observed waves exceed the criterion equal to 4 xrms. Therefore the events under consideration can be related to meteotsunami; at that, their energy is distributed almost all over the whole range of tsunami waves. When meteotsunami is absent, energy of the sea level oscillations in the range 4–120 min is reduced by an order. Since fluctuations are observed in the coastal zone possessing the resonant properties, arrival of meteotsunamis to these areas eventually results in exciting the seiches which are recorded. It is shown that in the coastal zone, cold fronts generate meteotsunamis, which, in their turn, give rise to seiches. Conclusions. The conditions for generating sea waves by the atmospheric disturbances within the range of the tsunami periods 2–120 minutes are described. It is found that movement of an extended cold front in the east-south direction leads to generation of the large-amplitude seiches in the region of the southern part of the Sakhalin Island, just where all the settlements are located. At a synoptic situation when two cold fronts are moving over the island, generation of high-amplitude seiches is possible in the places, near which a cold front is passing.

Seyshi, vyzyvayemyye atmosfernymi vozmushcheniyami v diapazone periodov meteotsunami, u poberezh'ya yuzhnoy poloviny ostrova Sakhalin

Purpose. The aim of the paper is to study four synoptic situations, in which the seiches energy in-crease was observed in the coastal zone of the southern part of the Sakhalin Island, and to consider their possible meteorological origin. Methods and Results. Records of the waves obtained in the Institute of Marine Geology and Geophys-ics in 2008 using both the instruments installed in eight points in the coastal zone of the southern part of the Sakhalin Island, and the synoptic maps provided by the Sakhalin Hydrometeorological Service Department, were used. For all the observation points, four synoptic situations characterized by in-crease of the seiches energy within the meteotsunami existence range were considered. It is shown that the amplitudes of the main part of the observed waves exceed the criterion equal to 4 xrms. There-fore the events under consideration can be related to meteotsunami; at that, their energy is distributed almost all over the whole range of tsunami waves. When meteotsunami is absent, energy of the sea level oscillations in the range 4–120 min is reduced by an order. Since fluctuations are observed in the coastal zone possessing the resonant properties, arrival of meteotsunamis to these areas eventually results in exciting the seiches which are recorded. It is shown that in the coastal zone, cold fronts generate meteotsunamis, which, in their turn, give rise to seiches. Conclusions. The conditions for generating sea waves by the atmospheric disturbances within the range of the tsunami periods 2–120 minutes are described. It is found that movement of an extended cold front in the east-south direction leads to generation of the large-amplitude seiches in the region of the southern part of the Sakhalin Island, just where all the settlements are located. At a synoptic situation when two cold fronts are moving over the island, generation of high-amplitude seiches is possible in the places, near which a cold front is passing.

Forecasting the Number of Passengers from Bakauheni Port during the Sunda Strait Tsunami Period Using Intervention Analysis Approach and Outlier Detection

The purpose of this study is to model and predict the number of ferry passengers from the Bakauheni port during the Sunda Strait Tsunami period. The Bakauheni-Merak crossing route is one of the sea crossing nodes serving crossings from Sumatra to Java and vice versa. The cruise line with a route length of 27.75 km serves both passenger and vehicle crossings. This route is the main route of logistics distribution from Java to Sumatra and vice versa. The tsunami that happened in the Sunda Strait on 22 December 2018 indirectly impacted the Sunda Strait sea crossing node especially the Bakauheni-Merak route. Methods that can be used to analyze the external impact of an event that causes changes in data patterns are Intervention Analysis and Outlier Detection. Both approaches are a type of Time Series method based on time series data. Therefore, this method can be used to model and predict the number of ferry passengers from the Bakauheni port during the Sunda Strait Tsunami period. If observed visually based on time series data patterns, the number of passengers from the port of Bakauheni has decreased for 2 days after the Tsunami. However, the number of passengers increased again on the Christmas holiday on December 25, 2018 or 3 days after the Tsunami. The tsunami that happened close to the Christmas holidays 2018 gave the results of initial identification, namely the existence of other events that caused changes in the pattern of passenger data. The event was a Christmas holiday on December 25, 2018. This research is expected to be able to capture and analyse phenomena that happen in a series of data during the Sunda Strait Tsunami period.

Pemodelan dan prediksi jumlah penumpang pelabuhan bakauheni selama periode tsunami Selat Sunda menggunakan autoregressive integrated moving average

Bakauheni Port is a ferry port located in Bakauheni District, South Lampung. This port is one of the major ports located on Sumatera island connecting Sumatera and Java and is located in the Sunda Strait. The tsunami that occurred in the Sunda Strait on December 22, 2018 indirectly affected the sea crossing node, especially the Bakauheni-Merak route. This can lead to changes in time series data patterns. The phenomenon is expected to be captured through a mathematical modeling that can be used as a decision making in the future. The purpose of this study was to model and predict the number of Bakauheni port passengers during the Sunda Strait Tsunami period using the Autoregressive Integrated Moving Average (ARIMA). The ARIMA approach uses past information as a basis for modeling. Based on visual information on the number of Bakauheni Port passengers, there was an increase in December in general. Other information is that there are seasonal patterns that occur with a span of 7 days. This was indicated by the pattern of repeated increases in the number of passengers every Sunday. After the tsunami, the number of passengers decreased for 2 days. In the 3 days after the Tsunami or during the Christmas holiday on December 25, 2018, the number of passengers has increased again. Based on the analysis and discussion that has been done, the best time series model obtained is ARIMA([5],1,2)(2,1,0)7 with a Mean Absolute Percentage Error (MAPE) of 9.55%.

Bizarre movements of Earth cause deadliest tragedies and Climate Change

A few deadliest catastrophes in the Asia-Pacific regions are Tsunami on 22.12.2004; Aila on 25.05.2009; earthquakes on 11.03.2011 and 25.04.2015; Tornados on 26.04.1989 and Cyclones on 12.11.1970. Very recently Cyclone Fani has smashed parts of Odisha and West Bengal in May 3 – 5, 2019, which has befallen due to climate change.The monitoring of rotational and orbital motions of the Earth is one of the key objectives of this research to observe whether those have any role behind these calamities. Since April 2005 data has been recorded, and analyzed data infers the climatic change. Comparative studies between the experiment and theory show that the earth was walking away during the period of tsunami 2011 to Kathmandu earthquake 2015. A bizarre etiquette of the earth has increased zenithto 0.3686° and rotational angle to 5.58° annually. If this state of affairs continues the local temperature will be 50° C in 2050.

Numerical modeling of the subaerial landslide source of the 22 December 2018 Anak Krakatoa volcanic tsunami, Indonesia

The eruption of the Anak Krakatoa volcano (Indonesia) in December 2018 produced a destructive tsunami with maximum runup of 13 m killing 437 people. Since the occurrence of this rare tsunami, it has been a challenge as how to model this tsunami and to reconstruct the network of coastal observations. Here, we apply a combination of qualitative physical modeling and wavelet analyses of the tsunami as well as numerical modeling to propose a source model. Physical modeling of a volcano flank collapse showed that the initial tsunami wave mostly involves a pure-elevation wave. We identified initial tsunami period of 6.3–8.9 min through Wavelet analysis, leading to an initial tsunami dimension of 1.8–7.4 km. Twelve source models were numerically modelled with source dimensions of 1.5–4 km and initial tsunami amplitudes of 10–200 m. Based on the qualities of spectral and amplitude fits between observations and simulations, we constrained the tsunami source dimension and initial amplitude in the ranges of 1.5–2.5 km and 100–150 m, respectively. Our best source model involves potential energy of 7.14 × 1013–1.05 × 1014 J equivalent to an earthquake of magnitude 6.0–6.1. The amplitude of the final source model is consistent with the predictions obtained from published empirical equations.

Hybrid Approach for Tsunami Protection: Effect of Embankment-type Seawall and Vegetation on Tsunami Reduction

A hybrid system for tsunami mitigation made up of a seawall and a vegetation belt (Pohutukawa trees) was numerically modeled and analysed to see how it performed under a simplified tsunami wave. The seawall and vegetation belt properties in the mitigation system were varied and subjected to different tsunami periods and beach slopes to reflect a New Zealand context. The modelling results suggest that larger seawalls in the mitigation system reduced tsunami inundation lengths thus run-up heights, and damage forces considerably more than smaller seawalls. Vegetation belts in the system did not contribute to reducing tsunami inundation lengths. Longer vegetation belts did however reduce the damage force of the tsunami. Individually, the seawall structure played a more significant role than the Pohutukawa vegetation belt in the mitigation system.

Possible Dual Earthquake\u2013Landslide Source of the 13 November 2016 Kaikoura, New Zealand Tsunami

A complicated earthquake (Mw 7.8) in terms of rupture mechanism occurred in the NE coast of South Island, New Zealand, on 13 November 2016 (UTC) in a complex tectonic setting comprising a transition strike-slip zone between two subduction zones. The earthquake generated a moderate tsunami with zero-to-crest amplitude of 257 cm at the near-field tide gauge station of Kaikoura. Spectral analysis of the tsunami observations showed dual peaks at 3.6–5.7 and 5.7–56 min, which we attribute to the potential landslide and earthquake sources of the tsunami, respectively. Tsunami simulations showed that a source model with slip on an offshore plate-interface fault reproduces the near-field tsunami observation in terms of amplitude, but fails in terms of tsunami period. On the other hand, a source model without offshore slip fails to reproduce the first peak, but the later phases are reproduced well in terms of both amplitude and period. It can be inferred that an offshore source is necessary to be involved, but it needs to be smaller in size than the plate interface slip, which most likely points to a confined submarine landslide source, consistent with the dual-peak tsunami spectrum. We estimated the dimension of the potential submarine landslide at 8–10 km.

Tsunami taxonomy and detection from recent Mediterranean tide gauge data

Sea level records, collected in digital form with high sampling rate by recently upgraded tide gauges located along the Mediterranean coasts, are subjected to a posteriori investigation to examine and characterize occurrence of sea level oscillations in the tsunami period range, induced by both underwater or coastal earthquakes and by meteorological events. After performing a rigorous quality control procedure on the raw sea level time series, a wavelet based analysis is applied to 2 h high-pass filtered data to identify oscillations generated by earthquakes, and a few events are modeled aiming to verify travel time and expected spectral shape. Seismic tsunami oscillations that are not reported in published catalogues are identified in the sea level records of the period 2010–2014 just after three different earthquake events. A method is proposed to detect occurrence of tsunami-like oscillations of meteorological origin from the available tidal records based on the distribution of the detided level process over spectral bandwidth parameter and mean period. The developed methodology is also the first presented which allows to distinguish sea wave induced harbor seiches from fluctuations of meteorological origin associated with passage of atmospheric disturbances (meteotsunamis) in sea level time series. The results of the analyses show that, during the considered period, in the Mediterranean Sea tsunamis of seismic origin are rare and weak; meteotsunamis on the contrary are relatively frequent and in critical areas may reach intensities exceeding astronomical tide. The availability of the recently acquired high frequency records and the presented approach allow to extend the list of recorded tsunami events of both seismic and meteorological origin. The identified event sets may be used for improved hazard analyses and risk assessments along the Mediterranean coasts.