According to United States Geological Survey (USGS)- “Earthquake waves or seismic waves are the vibrations that travels through the earth’s crust and mantle, caused by the sudden movement of rocks during an earthquake.”

Types of Earthquake waves –

• Body waves are seismic waves which travel through the earth’s interior and divided in to two types –

a) Primary Waves – These are compressional waves which travel through solid, liquid and gas .It causes ground compression and expansion.

b) Shear Waves -These are shear waves which travel only through solid materials.These are slower than primary waves.It causes ground deformation and shaking.

• Surface waves are seismic waves that travel along the earth’s surface and divided into two types-

a) Rayleigh waves- These are rolling waves and these are most destructive wabe type which causes ground motion in circular motion.

b) Love waves – These are horizontal waves which cause ground motion perpendicular to direction of travel.They are less destructive than Rayleigh waves.

Emergence of Shadow Zones – 

• Earthquake occurs and generation of seismic waves occurs (P,S Waves).
• Seismic waves travel through earth’s interior and along the surface.
• Waves interaction with Earth’s core , mantle, & crust.It will led to refraction, reflection, diffraction and absorption.
• Waves are blocked or significantly reduced in certain areas creating shadow zones –

a)P-Wave Shadow Zone (105° to 145 ° from epicenter).

b)S-Wave Shadow Zone (105° to 105° from epicenter).

Understanding these waves and shadow zones will help the scientists in studying earth’s internal structure , predicting earthquake behaviour and will improve their hazard assessment.

India has four seismic zones Zone I (low intensity), Zone II (low to moderate), Zone III (moderate to high) and Zone V (high intensity). Zones III and V cover Himalayan regions, Gujarat and parts of Maharashtra requiring special building codes.

Building codes and regulations mitigate earthquake damage in seismic zones through –

1.  Seismic resistant design ensures buildings withstand earthquake forces through flexible structures, reinforced materials and impact absorbing systems.
2. Structural reinforcement utilizes steel rebar, fiber mesh and advanced materials to enhance building strength and durability.
3. Foundation requirements include deep foundations, piles and specialized systems to transfer seismic forces to stable ground.
4. Regular inspections ensure compliance with seismic codes, identifying vulnerabilities and prompting corrective actions beforehand.
5. Material quality standards specify strength, durability and resilience requirements for steel, concrete and other construction materials.
6. Non structural element securing ensures partitions, ceilings, facades and equipment are anchored to prevent earthquake induced displacement.
7. Fire resistance requirements ensure buildings withstand post earthquake fires, protecting occupants and neighboring structures from spread.
8. Earthquake resistant systems utilize seismic isolation, damping and energy dissipation technologies to reduce building vibrations and stress.
9. Emergency evacuation routes provide clear, accessible escape paths, ensuring safe egress during and after earthquakes.
10. Early warning systems detect seismic activity by alerting occupants seconds before earthquake impact, enabling timely evacuation.

International initiatives such as the International Association of Seismology and Physics of the Earth’s Interior (IASPEI), Global Earthquake Model (GEM) and United Nations Office for Disaster Risk Reduction (UNDRR), promote global cooperation, standardize earthquake risk assessment and enhance disaster response capabilities.

International collaborations significantly enhance global earthquake research and response strategies in several ways i.e.

Research Advancements – 

1. Enhance earthquake research data sharing through standardized formats, open access databases and joint initiatives, facilitating seamless information exchange and accelerating discovery.
2. Establish standardized methodologies for earthquake research through harmonized data collection, analysis protocols and best practices, ensuring consistency, comparability and reliability of findings.
3. Enhance earthquake research through advanced modeling by integrating diverse datasets, sharing computational resources and expertise and developing sophisticated simulation techniques.

Improved response strategies – 

1. Enhance earthquake early warning systems through shared data, coordinated monitoring networks and standardized detection algorithms, enabling rapid alert dissemination and saving lives.
2. Enhance earthquake emergency preparedness plans by sharing best practices, conducting joint drills and developing harmonized response protocols, ensuring coordinated and effective disaster response.
3. Enhance earthquake search and rescue operations through coordinated deployments, shared resources, standardized communication protocols and joint training exercises, increasing effectiveness and saving lives.

International collaboration drives technological advancements in earthquake response through developments in AI powered early warning systems, high performance computing simulations, drones, satellite imaging and wearable sensors, enabling rapid damage assessments, targeted rescue efforts and enhanced disaster resilience globally.