Tsunami Period Research Articles

The Capital Investment Increases and Stock Returns

This paper applies free cash flow and information asymmetry hypotheses to investigate whether managers pursuit their private benefits by using capital investment expenditure (hereafter CI) increases or not, and to explore whether managers decrease CI as more dividend payments under information asymmetry hypothesis. Consequently, the present study investigates the effect of CI increases on abnormal stock returns of Taiwanese listed firms. The empirical results show that during full period and the post financial tsunami period, the effects of an increase in CI on stocks returns are positive, and the CI-spread is negative. This supports the hypothesis of information asymmetry. However, in the electronics industry during the entire study period and the post financial tsunami period, the expenditure of low CI tends to support free cash flow hypothesis but that of high CI supports the hypothesis of information asymmetry.

RETRACTED ARTICLE: Adaptive neuro-fuzzy estimation of bridge girder forces with perforations under tsunami wave loading

Tsunami disaster poses a great threat to coastal infrastructures. Bridges without adequate provisions for earthquake and tsunami loading is generally vulnerable to tsunami attack. During the last two disastrous tsunami event (i.e. Indian Ocean and Japan Tsunami) a number of bridges were observed subsequent damages by tsunami waves. Since it is very crucial problem in this paper was constructed a process which simulates the effects of perforations in bridge girder in force reduction with adaptive neuro-fuzzy (ANFIS) method. ANFIS shows very good learning and prediction capabilities, which makes it an efficient tool to deal with encountered uncertainties in any system like tsunami waves. Laboratory experiments were conducted to create experimental training and checking data for ANFIS network. This intelligent estimator is implemented using Matlab/Simulink and the performances are investigated. Results showed that significant amount of forces were reduced using perforations in girder. Approximately 10 to 18 % force reductions were achieved by using about 16 % perforations in bridge girder. Subsequent amount of force reductions revealed that perforations in girder are effective in reducing tsunami forces as perforations in girder let water to be passed through. Thus, less bridge damages are expected with the presence of perforations in girder during tsunami period. The simulation results presented in this paper show the effectiveness of the developed method.

Performance of Bridge Girder with Perforations under Tsunami Wave Loading

Tsunami disaster poses a great threat to coastal infrastructures. Bridges without adequate provisions for earthquake and tsunami loading is generally vulnerable to tsunami attack. During the last two disastrous tsunami event (i.e. Indian Ocean and Japan Tsunami) a number of bridges were observed subsequent damages by tsunami waves. In this study, laboratory experiments were conducted to study the effects of perforations in bridge girder in force reduction. Results showed that significant amount of forces were reduced using perforations in girder. Approximately 10% to 18% force reductions were achieved by using about 16% perforations in bridge girder. Subsequent amount of force reductions revealed that perforations in girder are effective in reducing tsunami forces as perforations in girder let water to be passed through. Thus, less bridge damages are expected with the presence of perforations in girder during tsunami period. Keywords—Bridge, force, girder, perforation, tsunami, wave.

Waveform and Spectral Analyses of the 2011 Japan Tsunami Records on Tide Gauge and DART Stations Across the Pacific Ocean

We studied the 11 March 2011 Tohoku tsunami through analysis of the sea level records from 21 tide gauge and 16 DART (Deep-ocean Assessment and Reporting of Tsunamis) stations from across the Pacific Ocean. The extreme power of this trans-oceanic tsunami was indicated by the trough-to-crest heights of 3.03 m at Arena Cove on the western coast of the USA and 3.94 m at Coquimbo on the southern coast of Chile. The average value of the maximum amplitude was 163.9 cm for the examined tide gauge records. At many coastal tide gauge stations the largest wave arrived several hours after the first arrival of the tsunami wave, and the tsunami lasted for a long time with an average duration of 4 days. On the contrary, at most of the DART stations in the deep ocean, the first wave was the largest, the tsunami amplitudes were smaller with an average maximum of 51.2 cm, and the durations were shorter with an average of 2 days. The two dominant tsunami periods on the DART records were 37 and 67.4 min, which are possibly attributed to the width and length of the tsunami source fault, respectively. The dimensions of the tsunami source was estimated as 233 km × 424 km. Wavelet analyses of tide gauge and DART records showed that most of the tsunami energy was distributed at the wide period band of around 10–80 min during the first hour after the tsunami arrival, then it was concentrated in a relatively narrower band. The frequency-time plots showed the switches and lapses of tsunami energy at the 35- and 65-min period bands.

Firm Size Transmission Effect and Price-Volume Relationship Analysis During Financial Tsunami Periods

Investors attend importance to forecast the price of financial assets, thus, the factors affecting the stock price are usually the focus of financial research in the field, in which the most important factors to scholars are firm size transmission effect and price-volume relationship. In this study, the analysis of these two items in the Taiwan stock market is conducted. The results indicate that the firm size transmission effect is almost significant, and the reversal phenomenon also exists. However, before the financial tsunami, the firm size transmission effect does not significantly exist; this result also indirectly proves the directional asymmetry of the market returns, proposed by McQueen, Pinegar, and Thorley (1996). For price and volume relationship, big cap index reveals that volume leads to price before the financial tsunami, and small cap index appears that price leads to volume in 2010.

Remote Sensing of Chlorophyll and Sea Surface Temperature in Indian Water with Impact of 2004 Sumatra Tsunami

The daily and weekly averaged Indian Remote Sensing satellite IRS-P4 Ocean Color Monitor (OCM) derived chlorophyll images were generated and interpreted in terms of pretsunami, tsunami, and posttsunami periods in the Bay of Bengal and Andaman Sea. There has been observation of increase in chlorophyll concentration up to 5.0 mg/m3 in the tsunami-affected coastal waters. The high chlorophyll concentration lasted for about one week after the tsunami catastrophe. The standard deviation for different transects in the tsunami-affected water were plotted. The high chlorophyll has been observed for selected transects in the aftermath of the tsunami event in coastal regions, and offshore water has also shown increase in chlorophyll concentration (∼1.0 mg/m3) in the Bay of Bengal. The analysis indicated that the tsunami waves might have displaced and spread the high chlorophyll coastal water towards offshore. NASA Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua daytime sea surface temperature (SST) daily images were retrieved and displayed during December 21, 2004, to January 6, 2005, and indicated the cooling (0.5–1°C) in the Bay of Bengal around Tamil Nadu and Andhra coast. The National Oceanographic and Atmospheric Prediction-National Center for Environment Prediction (NOAA-NCEP) data for five weeks (December 9, 2004–January 12, 2005) were retrieved to study the SST variability trend in prior to MODIS data and indicated 0.5–1°C cooling of the Bay of Bengal water off Kakinada, Chennai, Cuddalore, and Nagapattinam region on December 26 and 28, 2004.

The first results of long wave registration in the range of tsunami periods in the region of Kurilsk ridge on a distributed station network corresponding member of the RAS

The first results of long wave registration in the range of tsunami periods in the region of Kurilsk ridge on a distributed station network corresponding member of the RAS

MULTI- TEMPORAL STUDIES ON COASTAL WETLANDS OF VEDARANYAM COAST USING REMOTE SENSING AND GIS

Wetland, the prime component of the coastal zone is a dynamic ecosystem having complex inter-relationship of hydrology, soil and vegetation. They are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or land covered with shallow water. The coastal wetland of Vedaranyam, Tamil Nadu coast is a most productive ecosystem such as mangroves, salt marshes, lagoons and estuaries on the coastal area. It is extremely important as habitat for them. Due to increased anthropogenic activities, these ecosystems are under pressure on the coast. This leads to modification of wetlands ranging from various stages of degradation to irreversible loss. Spatial information has been propagated and is increasingly used for wetland management and conservation. The tsunami effect was extensive in and around Nagapattinam, but in Vedaranyam coastal wetland, located nearer to Nagapatinam (Nagapattinam district), the effect was less because of presence of mangroves. So it is necessary to protect this coastal wetland ecosystem to ensure sustainable development. Remote sensing has provided a great mean to study various ecosystems of the earth including wetlands by providing cost and time effective data. Over the years, remote sensing has been used as a tool to map large areas of wetlands. In this study, wetland change detection of the Vedaranyam coast within approximately eight years period was conducted. Three (IRS LISS III + PAN merged) images of different dates (1997, 2003 and 2005) were processed and analyzed, geometrically corrected (registered) and digitized to obtain more detailed information and identify the change. Based on the combined use of multi temporal satellite imagery and ancillary data, such as topographic maps and field check (ground truth) data, wetland maps with different classes were prepared, showing the changes, and usefulness of IRS data in detailed mapping and wetland change detection studies. The results showed that from 1997 to 2003, were found great loss of wetland and from 2003 to 2005 only inundated variation were studied at the period of tsunami in the study area.

Characteristic period of Tsunami in Seto Inland Sea

It is very important for tsunami disaster prevention in the coastal area of Shikoku Island to clarify a mechanism of tsunami propagation in the Seto Inland Sea. Especially, a resonance of tsunami is a dominant factor in such a narrow inland sea. In this study, numerical simulation of tsunami propagation is executed to estimate tsunami height and characteristic period in the Seto Inland Sea. According to the numerical analysis, a tsunami height does not decline during about 10 hours and a characteristic period of Harima-nada is about 60 minutes. The tsunami continued to be resonated for more than 20 hours in the Seto Inland Sea.

BACTERIOLOGICAL ANALYSIS OF WATER SAMPLES FROM TSUNAMI HIT COASTAL AREAS OF KANYAKUMARI DISTRICT, TAMIL NADU

Water borne diseases such as cholera, enteric fever and dysentery were expected after the tsunami, which hit the coastal areas of Kanyakumari district, Tamil Nadu. In the present study 151 drinking water sources were collected from the tsunami affected villages and relief shelters and tested for coliforms and pathogens. Nine well water samples were also collected for specific bacteriological analysis. Presence of coliforms was detected in 56 (37%) water samples. One isolate each of Salmonella Paratyphi B and NAG Vibrio were isolated from two well water samples. There was no report of acute diarroeal diseases or typhoid illness during the post tsunami period monitored by a field microbiology laboratory for a month.

Bacteriological analysis of water samples from Tsunami hit coastal areas of Kanyakumari District, Tamil Nadu

Water borne diseases such as cholera, enteric fever and dysentery were expected after the tsunami, which hit the coastal areas of Kanyakumari district, Tamil Nadu. In the present study 151 drinking water sources were collected from the tsunami affected villages and relief shelters and tested for coliforms and pathogens. Nine well water samples were also collected for specific bacteriological analysis. Presence of coliforms was detected in 56 (37%) water samples. One isolate each of Salmonella Paratyphi B and NAG Vibrio were isolated from two well water samples. There was no report of acute diarrhoeal diseases or typhoid illness during the post tsunami period monitored by a field microbiology laboratory for a month.

The 30 December 2002 landslide-induced tsunamis in Stromboli: sequence of the events reconstructed from the eyewitness accounts

Abstract. On 30 December 2002 the coast of the volcanic island of Stromboli, in the Tyrrhenian sea, Italy, was attacked by two tsunamis generated by landslides that took place on the north-west flank of the volcano. The landslides and the tsunamis represented the most impressive and threatening episodes of a strong effusive eruption, started on 28 December from a new vent which opened close to the north-east crater of the volcano. In spite of the intensified monitoring carried out in response to the eruption, the landslides and the ensuing tsunamis were not foreseen, and the available instrumental data are insufficient to allow a precise reconstruction of the sequence of the events. The seismic network recorded two main landslides along the steep slope of Sciara del Fuoco, with onset around 13:15 and 13:23 local time (GMT+1). The tsunamis were the direct consequence of the mass movements. Three main post-event surveys helped make assessment on the wave impact on the coast. In this paper the attention is focussed on the accounts of the eye-witnesses, that help us clarify and understand what happened. People in the source area (Sciara del Fuoco) reported a small-volume subaerial slide taking place first, then a sharp cut forming in the sea water down to the sea floor (about 10–20 m deep) and propagating almost parallel to the coastline, be concomitantly associated with a sea retreat and a subsequent sea advance. It is suggested here that the cut was the effect of a large submarine landslide that detached from very close to the coast and produced the 13:15 signal in the recorded seismograms. The second, mostly subaerial, slump was observed to slide down 7–8 min later and to excite a train of waves some distance offshore. Not all the witnesses realised that two distinct tsunamis occurred. The tsunami period was probably in the order of 100 s, but shorter period crests were seen to travel on the top of the long-period waves by several persons. The duration of each tsunami was appreciated to be around 5–7 min. It is difficult to ascertain which tsunami was the largest, since there is no full agreement among the observers, but certainly by accounts both were characterised by large destructive waves.

Analytical evolution of tsunamis induced by near-shore earthquakes on a constant-slope ocean

Strong near-shore earthquakes are the most frequent sources of tsunamis in many oceans of the world. In the framework of the nonlinear shallow-water theory, the initial sea-surface tsunami elevation is assumed to equal the sea-floor co-seismic displacement produced by the seismic event. This is quantified by means of the analytical formulas due to Okada (1985, 1992), dealing with seismic faults buried in an elastic medium. In this work the propagation of tsunamis is studied along two-dimensional profiles on an idealized constant-slope sea bed, an approximation that allows one to reduce the governing nonlinear equations to a linear problem by means of the classical Carrier & Greenspan (1958) approach. We introduce an analytical solution that is sufficiently general to account for initial conditions associated with paradigmatic cases of sea-bottom deformations produced by near-shore earthquakes, such as subsidence or uplift of the coastal area, and can be also used to treat more complex deformations. The main result is that the amplification of the tsunami height at the coast is found to range between approximately 1 and 2. The amplification is around 1 for tsunamis induced by earthquakes with their epicentre inland and tends to grow as the fault moves seaward. We restrict our analysis to earthquakes that dislocate the shore region. Within the class of sources that we consider, the tsunamis that are most amplified are the ones having initial profiles with a crest–trough–crest system or conversely with a trough–crest–trough system. The bottom slope is found to have no effect on tsunami run-ups and run-downs, but to influence tsunami periods and tsunami speed remarkably. Breaking analysis shows that wave breaking does not occur if the initial wave height is less than 8–9 m, and that the simplest sea-level profiles, which are associated with earthquakes with their epicentre on land, are not expected to break even if their initial height exceeds 19 m.

Air‐sea interaction and feasibility of tsunami detection in the open ocean

Recent observations of “tsunami shadows,” i.e., extended darker strips on the ocean surface along a front of a weak tsunami off Oahu, Hawaii, suggest that tsunamis in the deep ocean may be remotely detected through changes in ocean surface roughness. In this paper, physical mechanisms responsible for the formation of “tsunami shadows” are considered. The hypothesis that the change in surface roughness is due to an air‐sea interaction is examined. Using an eddy‐viscosity model for the average Reynolds stresses in turbulent flow, a theory is developed to model tsunami‐induced perturbations in the atmospheric boundary layer. It is demonstrated that in the lowest tens of centimeters of the atmosphere, tsunami‐induced perturbations of the mean wind velocity are much greater than current velocities in the water and can be comparable to the unperturbed wind velocity. Enhancement of tsunami‐induced wind velocity perturbations compared to currents in the tsunami wave occurs because of a generation of a viscous wave in the air by a coherent elevation of large expanses of the ocean surface in the tsunami wave. The ratio of the maximum wind velocity perturbation to the amplitude of the current velocity approximately equals (πD/4κ2λ) ln2 (κu*λ/2πcz0), where κ is the von Kármán constant, u* is the friction velocity of a background wind, z0 is the roughness length of the ocean surface, D is ocean depth, and λ and c are the tsunami wavelength and velocity, respectively. The results are shown to be robust with respect to a choice of a closure model for Reynolds stresses. Dependence of the tsunami‐induced atmospheric perturbations on background wind velocity and direction, tsunami period and amplitude, and ocean depth is studied. Implications of the theoretical predictions on the feasibility of a satellite‐based system relying on radars and/or microwave radiometers for early tsunami warning are discussed.

Relationships of tsunami generation and an earthquake source.

This paper presents a theory of tsunami generation and propagation on a spherically symmetric, self-gravitating, elastic Earth in terms of normal modes. We predict the character of newborn tsunamis at regional far field distances from a simply parameterized moment tensor point source with step function time history. Tsunami eigenfunctions are shown to penetrate the Earth from tens of kilometers at 2, 000 second period to tens of meters at 20 second period. This behavior explains why the longest tsunami periods are the only ones influenced by crust and mantle structure and why they are preferentially excited by submarine earthquakes. We find that large tsunamis need sizable parent earthquakes because over 96% of their energy is concentrated in the ocean. This makes the entire solid Earth virtually a node for tsunami generation. The excitation of tsunami modes is strongly dependent upon the moment, mechanism and depth of faulting. Calculated tsunami energy, ET, can vary by a factor of 100 for sources of equal moment within 30 kilometers of the sea floor. Maximum ET for dip slip and strike slip faulting with moment M0=1020N·m is 1.5×1013 and 1.1×1012 joules. With mechanism and depth fixed, this source model predicts that ET is proportional to M02. The ratio of tsunami to radiated seismic energy is less than 1% for all but the largest events. We believe that this theory coupled with a seismic source recovery technique could be a realistic basis for the forecasting of potentially dangerous tsunamis in real time.

Tide Gage Frequency Response

Theoretical calculations of the frequency response of a tide gage stilling well are made, and compared with recorded tsunami heights and periods. While the frequency response only affects very short-period, large-amplitude tsunamis, the nonlinearity of the response (i.e., dependence on amplitude) places limitations on the interpretation of spectra obtained from tide gage records. The nonlinear interaction between the orifice used as a filter on the stilling well and Stokes' second-order waves is calculated numerically for a steady-state case, and is shown to result in small errors in the tide gage reading. The possibility of the transient case resulting in spurious seiche or surf beat records from groups of higher waves is suggested.