Tsunamigenic Earthquakes

The geomorphologic and archaeological research that currently is being developed in the Odiel Marshland Nature Reserve −Biosphere Reserve by UNESCO−, especially in the sand barrier of La Cascajera, have provided interesting results that allow know about the occupation of Huelva coast in Roman times from a diachronic point of view in the transition from Late Empire to the Late Antiquity. In that respect are numerous fish salting plants (cetariae) that dot the western coast of the former province Baetica and which now after a review process, it can sense or see moments of breakdown and recovery in their holdings should be put in relation to extreme wave events (EWE) that historically have affected these shores.

In the present work, an advanced tsunami generation, propagation and coastal inundation 2-DH model (i.e. 2-D Horizontal model) based on the higher-order Boussinesq equations – developed by the authors – is applied to simulate representative earthquake-induced tsunami scenarios in the Eastern Mediterranean. Two areas of interest were selected after evaluating tsunamigenic zones and possible sources in the region: one at the southwest of the island of Crete in Greece and one at the east of the island of Sicily in Italy. Model results are presented in the form of extreme water elevation maps, sequences of snapshots of water elevation during the propagation of the tsunamis, and inundation maps of the studied low-lying coastal areas. This work marks one of the first successful applications of a fully nonlinear model for the 2-DH simulation of tsunami-induced coastal inundation; acquired results are indicative of the model's capabilities, as well of how areas in the Eastern Mediterranean would be affected by eventual larger events.

Understanding the tsunami cycle requires a simple method for identification of tsunami backwash deposits. This study investigates Fourier transform infrared (FTIR) spectroscopy followed by careful analysis of variance (ANOVA), Gaussian distribution, hierarchical cluster analysis (HCA) and principal component analysis (PCA) for the discrimination of typical marine sediments and tsunami backwash deposits. In order to test the suitability of FTIR spectra as innovative methods for classifications of tsunami deposits, typical marine sediments and terrestrial soils were classified into three zones, namely zone-1 (i.e. typical marine sediments), zone-2 (i.e. including tsunami backwash deposits) and zone-3 (i.e. coastal terrestrial soils). HCA was performed to group the spectra according to their spectral similarity in a dendrogram and successfully separate FTIR spectra of all three sampling zones into two main clusters with five sub-clusters. The simplicifolious (i.e. single-leafed) type of dendrogram was observed with the strong dissimilarity of terrestrial components in subcluster- 5. Graphical displays of PC1 vs PC2 highlight the prominent features of zone-1, which is explicitly different from those of zone-2 and zone-3. The acceptable discrimination of typical marine sediments and tsunami backwash deposits, even six years after the tsunami on Boxing Day 2004, dramatically demonstrates the potential of the method for the identification of paleotsunami.

Over the past few years, several attempts have been performed to find alternative “chemical proxies” in order to discriminate “tsunami backwash deposits” from “typical marine sediments”. A wide range of statistical tools has been selected in order to investigate the sediments and/or terrestrial soils transportation mechanism during the tsunami inundation period by using several types of chemical tracers. To relate the physical and chemical characteristics of Typical Marine Sediments (TMS),Tsunami Backwash Deposits (TBD), Onshore Tsunami Deposits (OTD) and Coastal Zone Soils (CZS) with their synchrotron radiation based micro-X-ray Fluorescence (μ-SXRF) spectra, the μ- SXRF spectra were built in the appropriate selected spectra range from 3,000 eV to 8,000 eV. Further challenges were considered by using the first-order derivative μ-SXRF spectra coupled with Probability Distribution Function (PDF), Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) in order to investigate the elemental distribution characteristics in various types of terrestrial soils and marine sediments. Dendrographic classifications and multi-dimensional plots of principal components (i.e. bi-polar and three dimensional plots) could indicate the impacts of terrestrial soils and/or marine sediments transport on onshore and/or offshore during the tsunami inundation period. Obviously, these advanced statistical analyses are quite useful and provide valuable information and thus shed new light on the study of paleotsunami.

(In English) Sulawesi, one of the biggest island in Indonesia, located on the convergence of two macro plate that is Eurasia and Pacific. NOAA and Novosibirsk Tsunami Laboratory show more than 20 tsunami data recorded in Sulawesi since 1820. Based on this data, determination of correlation between tsunami and earthquake parameter need to be done to proved all event in the past. Complete data of magnitudes, fault sizes and tsunami heights on this study sourced from NOAA and Novosibirsk Tsunami database, completed with Pacific Tsunami Warning Center (PTWC) catalog. This study aims to find correlation between moment magnitude, fault size and tsunami height by simple regression. The step of this research are data collecting, processing, and regression analysis. Result shows moment magnitude, fault size and tsunami heights strongly correlated. This analysis is enough to proved the accuracy of historical tsunami database in Sulawesi on NOAA, Novosibirsk Tsunami Laboratory and PTWC.

Keywords: tsunami, magnitude, fault, height

(In Bahasa) Pulau Sulawesi terletak pada pertemuan antara tiga lempeng besar yaitu lempeng Indo-Australia, lempeng Pasifik dan lempeng Eurasia. Posisi demikian tentunya rawan terhadap gerakan dan benturan ketiga lempeng tersebut. Berdasarkan rekaman data bencana gempa dan tsunami Sulawesi yang berfrekuensi tinggi tersebut, maka kajian hubungan parameter luas sesar dengan magnitudo dan ketinggian tsunami perlu dilakukan untuk membuktikan parameter gempa dan tsunami di masa lalu dan perkiraan di masa mendatang.

Pada penulisan ini digunakan data gempabumi dan tsunami daerah Sulawesi yang diambil dari katalog WinITDB (PTWC) untuk mendapatkan data magnitudo dan ketinggian tsunami. Melalui tulisan ini, penulis mencari nilai hubungan antara magnitudo gempa dengan parameter luasan sesar dan hubungan antara ketinggian tsunami dengan parameter luasan sesar dengan mencari garis regresinya. Tahapan yang dilakukan dalam penulisan ini adalah pengambilan data, pengolahan data yang selanjutnya akan dilakukan analisis untuk mendapatkan hubungan antara magnitudo gempa dengan parameter luasan sesar serta hubungan antara ketinggian tsunami dengan parameter luasan sesar. Setelah diperoleh parameter luasan sesar dibuat grafik hubungan antara magnitudo dengan dengan luasan bidang sesar  kemudian diregresikan secara linier dan grafik antara luasan bidang sesar dengan ketinggian tsunami kemudian diregresikan secara logaritmik.

Berdasarkan pengolahan dan analisis data dapat ditemukan hubungan bahwa semakin besar nilai magnitudo momen (Mw), maka semakin besar nilai panjang (L), lebar (w), luas (S) dan slip (U) sesar yang terbentuk ; Semakin besar nilai magnitudo momen, maka semakin tinggi gelombang tsunami yang dihasilkan ; dan Semakin tinggi gelombang tsunami yang dihasilkan, maka semakin besar panjang (L), lebar (w), luas (S) dan slip (U) sesar yang membangkitkan tsunami.

Kata Kunci: tsunami, magnitudo, sesar, ketinggian

On September 16, 2015, a Mw 8.3 earthquake occurred off the coast of Illapel, Central Chile, generating a tsunami that caused moderate damage along the coast of Central Chile. To investigate tsunami damage and evacuation responses, we conducted a post-tsunami field survey between La Serena and Concón. The average tsunami inundation height in the survey area was 3–4 m; however, in the innermost corner of Coquimbo Bay, which was shielded from the tsunami source by the Coquimbo Peninsula, the tsunami inundation height was 6.0-6.2 m, decreasing gradually along the coast away from the corner. This phenomenon was also confirmed around Tongoy Bay, which is geographically similar to Coquimbo Bay. Based on our results, we hypothesize that the tsunami was diffracted and refracted by the peninsula, and then converged on the innermost corner of the bay, located behind the peninsula. Interviews with local residents confirmed that most people evacuated immediately after feeling strong seismic motion, but before the tsunami warning and evacuation orders were issued. However, several people did not evacuate, either because they believed that they were located in a safe place, or because they wanted to protect their property.

Coast. Eng. J. DOI: http://dx.doi.org/10.1142/S0578563416500030

Scenarios represent a very useful technique for the definition and evaluation of tsunami hazard and risk for any given region, and a basic step in the frame of tsunami mitigation and preparedness and of sustainable coastal zone development. With the exception of very few countries, like Japan and the United States, emergency plans in the rest of the world have never taken serious care of tsunamis until the occurrence of the giant Indian Ocean tsunami on December 26, 2004. That event dramatically brought the problem of tsunami hazard and risk assessment to the general attention and showed the urgent need for implementation of tsunami early warning systems (TEWSs). The problem is particularly urgent for the Mediterranean countries that are known to have been attacked by numerous tsunamis in the past, several of which had catastrophic size and impact. This paper is an attempt to develop some simple scenarios of earthquake-generated tsunamis in the Mediterranean. We identify four different seismogenic areas in the western, central and eastern sectors of the basin. For each of them, we take into account a seismic fault capable of generating an earthquake with magnitude equal or larger than the highest magnitude registered in that region in historical times. Then we simulate numerically the ensuing tsunamis, highlighting the basic features of the wave propagation and roughly identifying the coastal sectors that are expected to suffer the heaviest tsunami effects. One of the most important outcomes is that these scenario tsunamis attack the nearest coasts within at most 15 minutes, which poses serious constraints for designing appropriate TEWS for the Mediterranean.