marble. The implication is that the acidic rain causes faster weathering and dissolution of the building material which is more permanent. 2.3.7 Solar radiation Hadjibiros (2014) posits that solar radiation supplies sufficient energy to facilitate various photochemical reactions, for instance, breaking down of chemical compounds of nitrogen oxides and other volatile hydrocarbons. Likewise, the energy from solar radiation further causes electrons on objects to be excited leading to their break away from their constituent atoms. A separate research by Llop et al. (2013) further highlights that stone heritage is severely affected by atmospheric including solar radiation, rain and wind. The author also reports that solar radiation causes stress on the materials and leads to structural damage as they might dry out or become crazed and cracked. 2.3.8 Vibration Natural occurring vibrations arise from aspects such as earthquakes, ocean waves and wind and have an adverse consequence on the built environment by causing distress and movement (Smith, 2013). Likewise, manmade or artificial vibrations arising from traffic on rail and roads as well as sonic booms also exert impact on the built heritage as they can cause disintegration and other forms of damage throughout developed structure (UNESCO, 2008). More severe vibrations such as 8th degree earthquakes are also likely to cause severe consequences such as the demolition of walls (Petrini and Save, 2014). The authors add that 9 th and 10th degree earthquakes cause higher damage as they can reduce walls to rubble.
2.4 Social factors 2.4.1 Fire Toniolo, Boriani and Guidi (2015) posit that uncontrolled fire has a lasting effect on built heritage as it causes significant irreparable damage. UNESCO (2008) further adds that although there is a possibility of replicating the destroyed parts of the buildings, the damage from fire causes the loss of the original historic fabric of the building which makes it stand out. Figure 5 below illustrates Shuri Castle in Tokyo before a fire accident destroyed the heritage site.
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