# Vulnerability Assessment of Ubiquitous Cities Using the Analytic Hierarchy Process
## 2 The Components of U-Cities and Hazards
### Hazards to a U-City
#### 2.4.2 Natural Hazards  
A natural hazard is an occurrence of disturbing climatic conditions which adversely affects and endangers human lives. These hazards also implement risks of damaging different U-cities' technologies in different ways.  
Blizzard: Extreme low temperatures might influence the wired connection, heavy snowfall can weaken the wireless and satellite signals [65].  
Earthquake: Earthquake can easily destroy infrastructures and even landscapes. Technologies that rely on large scale underground cables such as BCN and IPv6 will be easily damaged, while wireless and small devices are less likely to be influenced. Far distance signal transmitting like GNSS is not affected by the earthquake at all. Therefore, satellite technology and wireless communications are often used to network seismic stations and monitor seismic activity [66].  
Flood: Similar to earthquakes, floods cause major damage to the ground and underground infrastructures but has more impact on electronic devices without waterproofs.  
Lightning: A lightning strike occurs when a huge amount of energy released by a spontaneous electricity discharge from the atmosphere. It causes physical damage to the power grid and communication facilities such as power line and radio tower, leads to large-scale blackout, affects the communication network, potential electronic devices malfunctions [67].  
Hailstorm: Technologies that most vulnerable to hailstorms will be fragile objects installed on rooftops since the damage is usually caused by gravitational forces. Devices and sensors with glass components or solar panel parts have a higher chance to be damaged. For example, traffic control signals and solar panels on the streetlight pole [68].  
Heat Wave: Opposite to blizzard, heatwave occurs with extreme heat for extended periods. Extreme high temperatures might influence the wired connection and slow down the internet [69].  
Hurricane/Typhoon: Hurricanes and typhoons consist of heavy rainfall, rapid temperature changes, and extreme wind speed. Small, lightweight outdoor devices or installations have a high chance to be damaged, Wi-Fi and radio signals are weakened, and result in slow internet. Also, it often leads to flooding and lighting [70].  
Solar storm: Solar storm contains charged particles by sending Coronal Mass Ejections (CMEs), which can disrupt satellites and electronic devices on Earth, with the potential to affect the power grid, internet, telecommunications, and navigation system [71].  
Tornado: The wind speeds of a tornado can excess 480 km (300 miles) per hour, infrastructure and objects especially power lines and small devices are easily destroyed by the shear forces and debris [72].  
Tsunami: Tsunami can cause an earthquake, volcanic eruption, or landslide. These powerful tidal waves often lead to devastating destruction to the coastal area and flood the affected area for a period. Most wire connections, electronic devices, and equipment would be destroyed [73].  
Volcanic eruption: An unstoppable natural disaster that can destroy any structures, change the landmasses, cover the atmosphere with smoke and dust, this results in poor phones and radios signals reception. Volcanic eruption often associates with earthquakes and lightning [74].  
Wildfire/Bushfire: Wildfire, or bushfire, is a large-scale uncontrolled blaze that consumes all flammable objects in its path. Wildfire can disable the communication network follow by the destruction of cables, radio signal towers, and the smoke and heat can inference satellites accuracy [75].  
Others: Hazards such as avalanches, drought, and meteoroid strikes have a serious impact on humans.