M$2$ Analyze the structural and environmental challenges associated with retrofitting aging infrastructure in earthquake$-$prone regions. Focus on the integration of advanced materials and seismic retrofitting techniques to enhance the resilience and longevity of critical structures such as bridges, highways, and public buildings. Discuss the economic implications, including cost$-$benefit analysis, funding mechanisms, and long$-$term maintenance considerations. Additionally, evaluate the regulatory frameworks and policy measures necessary to support these retrofitting projects, and explore the role of public awareness and community engagement in ensuring successful implementation. How can engineers balance the technical requirements with the socio$-$economic impacts to achieve sustainable and resilient infrastructure upgrades?