Seismic retrofit imminent problem, various research work has been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)'s guidelines. These codes must be regularly updated; the 1994 Northridge earthquake brought to light the brittleness of welded steel frames, for example. The retrofit techniques outlined here are also applicable for other natural hazards such as tropical cyclones, tornadoes, and severe winds from thunderstorms. Whilst current practice of seismic retrofitting is predominantly concerned with structural improvements to reduce the seismic hazard
Seismic noise Seismic noise In geology and other related disciplines, seismic noise is a generic name for a relatively persistent vibration of the ground, due to a multitude of causes, that is a non-interpretable or unwanted component of signals recorded by seismometers. Physically, seismic noise consists mostly of surface waves. Low frequency waves (below 1 Hz) are generally called microseisms; high frequency waves (above 1 Hz) are called microtremors. Its causes include nearby human activities (such as traffic or heavy machinery), winds and other atmospheric phenomena, and ocean waves. Seismic noise is relevant to any discipline that depends on seismology, such as