**2.1. Tsunami sources**

The recent advances in tsunami study has lead the scientist for better understanding of the cause of tsunami, its propagation and most importantly the system of warning ahead of tsunami arrival to the vulnerable coastal area. In addition, now the secondary sources for strengthening the devastating effect of the tsunami, for example, the splay faulting, landslide caused by the parent earthquake sources, have been advancing [3].

The main source for tsunami generation, however, has been identified as being the earthquake. Due to this, we will discuss here two case studies, namely the Makran (Indian Ocean) and Great East Japan earthquake and tsunami Pacific Ocean.

The other sources are classified as meteorological effects, meteotsunami. This has been discussed fully within this book on Chapter 1, and the underwater volcanic eruption as other tsunamigenic sources also being better documented and investigated on Chapter 2 of this book.

Tsunamis can also be generated by a submarine landslide, which typically occurs as a result of an earthquake [4]. A submarine landslide, rock fall or ice fall can trigger a tsunami by displacing large amounts of water. As a result, the water level rises generating tsunami.

The Papua New Guinea tsunami of July 1998 is a good example of relatively small deepwater submarine landslide, which caused devastating local tsunamis. This was triggered by a magnitude 7.1 earthquake [5]. The multibeam bathymetric study is a very useful tool in identifying this type of potential submarine landslide offshore.

The other sources of major risk contributors are the onshore earthquake events rather close to sea. The thick sediments at Oman Sea provide conditions for submarine landslides and slumps that can generate small tsunamis in the region. Heidarzadeh and Satake [6] showed that the tsunami observed in the northwestern Indian Ocean following the 23 September 2013 Pakistan inland earthquakes was generated by a submarine landslide.

In addition, the splay faults mapped offshore Makran can also play an important role as tsunami strengthening factor after the major tsunamigenic event has occurred, but not as independent tsunami source [7–9].

It is very important to note that the coastal area can be affected by both local and remote-source tsunami. In the case of a local earthquake, the impact of the earthquake can be greater than the tsunami. The main tsunamigenic earthquake may cause damages to buildings and infrastructure before the arrival of the tsunami wave, with potential loss of life. Therefore, in the near coast (local) tsunami-prone area, both tsunami and earthquake effect must be considered.
