Seismic Resilience: Do Old Houses From the 20th Century or Earlier Withstand Quakes Better Than Modern Structures?
Many people wonder if old houses from the 20th century or earlier were built to withstand earthquakes better than modern structures. While it might seem intuitive that older structures would be more resistant to seismic activity due to their historical standing, the reality is not as straightforward.
Modern Improvements in Seismic Engineering
Generally speaking, no, houses from the early 20th century or earlier were not built to withstand quakes better than modern structures. The structural integrity of houses built before the mid-1900s was largely dependent on the knowledge and craftsmanship of the individual builder, supplemented by a significant element of luck.
The introduction of building codes and inspections based on systematic real-world research has dramatically increased the structural reliability of houses in any area. These codes are continuously evolving, driven by ongoing research and updated based on lessons learned from each major earthquake. It is mainly within the last 40 years that the findings related to seismic activity, such as foundation and roof strapping, designed slip points, and box-beam corners, have been integrated into modern building standards.
Comparative Analysis of Building Materials and Techniques
Some traditional construction methods, such as post-and-beam with nonstructural infill or shell walls, have actually been found to handle seismic activity better than other methods. However, overall, structures from the pre-1900s era were a hit-or-miss proposition, with modern structures providing more reliable safety.
For instance, in earthquake-prone regions like New Zealand, traditional houses were commonly constructed from wood. Wood is superior to stone or brick in terms of absorbing movement. Once a stone or brick wall ruptures, the structure is irreparably compromised. Wood-frame construction, characterized by its lightweight and flexible nature, has shown better performance during seismic events. This is why much of our modern understanding of seismic resistance is based on studying traditional wood joints and applying them to steel framing.
Global Perspectives and Lessons Learned
While regions like Tokyo in Japan have experienced relatively safe and resilient buildings made of wood, it is not a universal truth. In regions where earthquakes are not frequent, buildings do not need to be earthquake-proof. Therefore, the focus on stringent construction codes and building design is mostly concentrated in areas with high seismic activity.
For seismically active areas such as Seattle, which experienced the 1906 Great San Francisco earthquake, modern houses are vastly different in their seismic resilience. Buildings from the early 20th century must be reinforced and often bolted to their foundations to withstand the forces of an earthquake. Our knowledge and calculations of the forces involved have become more precise over time, leading to significant improvements in seismic resistance.
Conclusion
The evolution of seismic resilience in building structures is a story of continuous improvement and adaptation. Each major earthquake provides new lessons that update our understanding and lead to better building codes. While some older construction techniques might still have advantages, the overall resilience of modern buildings has been significantly enhanced due to advanced research and ongoing updates to building standards.