Preface

The supercontinent Pangaea was formed by continental blocks that broke up about 250 million years ago to form Gondwana and Laurasia. The idea that Earth's continental blocks once formed a single supercontinent was proposed in 1912 by the German meteorologist Alfred Wegener in his "continental drift" theory in his 1915 book, *The Origin of the Continents and Oceans*. Wegener believed that this continental drift explained why the borders of South America and Africa fit together. He also highlighted the similar rock formations and fossils on these two continents. His idea, however, lacked a suitable mechanism explaining how the continents move. The geodynamic processes of the opening and closing of oceans along old orogenic belts were described by Wilson (1966) in his article "Did the Atlantic Close and then Re-Open?" published in *Nature*. Wilson argued that the Appalachian–Caledonide belt along the eastern margin of North America and Western Europe was formed by a "Proto-Atlantic Ocean." The idea that radioactive minerals within the mantle produce radiogenic heat as the driving force of convection currents was proposed by Arthur Holmes. In 1960, Harry Hess proposed his theory of seafloor spreading to account for the origin of oceanic ridges. In 1963, the Vine–Matthews–Morley hypothesis confirmed Hess' hypothesis. From 1950 to the 19070s, new data obtained from magnetic and paleomagnetic studies gave numerical parameters on the orientation of continental blocks.

The development of earth science over the last century has made it possible to image the Earth's interior using geophysical and geological data and computer modeling of magnetic, electric, and gravitational fields, as well as the propagation of seismic waves and the formation and deformation of rocks. Plate displacement across plate boundaries was successfully determined with GPS networks, while the development of computer systems gave rise to accurate plate reconstructions. A powerful geophysical imaging method is seismic tomography which enabled the mapping of lateral heterogeneities due to seismic velocity.

This book presents research methods based on field and laboratory studies combined with geodynamic and tectonic outputs. Section 1, "Crustal Evolution and Tectonic Problems," includes three chapters. Chapter 1 examines the tectonic evolution of the Himalayas since the Paleoproterozoic Era. Chapter 2 discusses the geodynamic evolution of the Iranian block during the Cretaceous Period and the importance of the Sabzevar-Nain Basin according to the results of a geological field study. Chapter 3 presents a case study on applying the phase stripping method to the tectonic phases of Southwest Japan to characterize the active fault structures. Section 2, "Geophysical Methods in Geological Applications," includes three chapters. Chapter 4 is a study showing a compilation of heat flow measurements, seismic tomography, seismicity, and hot spring distribution in Taiwan for understanding the relationship between the tectonic and geothermal potential in the study area. Chapter 5 presents an extensive paleomagnetic study carried out on Precambrian basement rocks in southwestern Nigeria to show the paleomagnetic pole movement. Chapter 6 shows the structural features of the Sokoto Basin in northwestern Nigeria using a potential field gravity method. Section 3, "Seismic Forecasting, Seismotectonics and Geodynamic Evolution of the Himalayan Belt," includes three

chapters. Chapter 7 presents a seismic hazard assessment done using GPS data in the Northwest and Central Himalayan regions. Chapter 8 applies a Brownian passage-time distribution as a seismic forecasting model for earthquakes. Finally, Chapter 9 discusses seismic risk in eastern Caucasia.

#### **Dr. Mualla Cengiz** Professor, Istanbul University-Cerrahpaşa, Department of Geophysical Engineering,

#### **Dr. Savaş Karabulut**

Istanbul, Turkey

Profesor, Gebze Technical University, Department of Civil Engineering, Kocaeli, Turkey Section 1
