Rising from the opposite side of the Golden Horn is another, conical hill, where the modern Beyolu district is situated. Because of the topography, buildings were once constructed with the help of terraced retaining walls (some of which are still visible in older parts of the city), and roads in Beyolu were laid out in the form of steps. Üsküdar on the Asian side exhibits similarly hilly characteristics, with the terrain gradually extending down to the Bosphorus coast, but the landscape in emsipaa and Ayazma is more abrupt, akin to a promontory. The highest point in Istanbul is Çamlca Hill (also on the Asian side), with an altitude of 288 meters (945 ft).Istanbul is situated near the North Anatolian Fault on the boundary between the African and Eurasian plates. This fault zone, which runs from northern Anatolia to the Sea of Marmara, has been responsible for several deadly earthquakes throughout the city's history. Among the most devastating of these seismic events was the 1509 earthquake, which caused a tsunami that broke over the walls of the city, destroyed over 100 mosques, and killed more than 10,000 people. More recently, in 1999, an earthquake with its epicenter in nearby zmit left 17,000 people dead, including 1,000 people in Istanbul's suburbs.[67] Istanbulites remain concerned that an even more catastrophic seismic event may be in Istanbul's near future, as thousands of structures recently built to accommodate the city's rapidly increasing population may not have been constructed properly.[67] Seismologists say the risk of a 7.6-magnitude earthquake striking Istanbul by 2030 is greater than sixty percent.
Climate
Istanbul has a Mediterranean climate according to the Köppen climate classification system, although its climate becomes more oceanic toward the north In summer the weather in Istanbul is hot and humid, with the temperature in July and August averaging 23 °C (73 °F). Summers are relatively dry, but rainfall is significant during that season.Extreme heat, however, is uncommon, as temperatures rise above 32 °C (90 °F) on only five days per year on average During winter it is cold, wet and often snowy, with the temperature in January and February averaging 4 °C (39 °F).