Unusual Delhi Earthquake: What Caused The Deafening Noise Before The Tremors?

People in Delhi and its outskirts were jolted awake by a 4.0-magnitude earthquake at 5:36 AM on February 17, 2025. The epicentre was five kilometres beneath the Earth’s surface near the Durgabai Deshmukh College of Special Education in Dhaula Kuan. Following this earthquake, which resulted in a surprisingly loud roar and felt ground shaking, people wondered about the cause of this auditory phenomenon.

Understanding the Loud Noise During the Delhi Earthquake

The sound heard by most people at the time of the earthquake is due to the characteristics of seismic waves produced at the time of the quake. Earthquakes generate two main types of body waves that move within the interior of the Earth:

1. Primary Waves (P-Waves): These are compressional waves where the vibration of the rock is in the direction of wave propagation. P-waves travel the fastest and are the first to arrive at a given location. At high frequencies, P waves can produce sounds audible to the human ear, similar to how sound waves travel through air.
2. Secondary Waves (S-Waves): These are shear waves where the rock oscillates perpendicular to the direction of wave propagation. S-waves travel slower than P-waves and typically do not produce audible sounds but contribute to the shaking felt during an earthquake.

In the case of the Delhi earthquake, the shallow depth of the seismic event meant that the P-waves had less distance to travel to the surface, retaining much of their energy. As these waves reached the surface, their high-frequency components became audible, resulting in the loud “boom” or rumbling noise reported by residents. This effect is more potent in shallow earthquakes since deeper earthquakes dissipate more high-frequency energy along the path to the surface.

Resident Experiences

The suddenness with which the tremors occurred, along with the sound that they produced, evoked mass fear. Anil Kumar, a resident of Sita Ram Bazar, asserted, “I felt a serious vibration and feared.” My wife and I also woke up my child immediately and ran outside.” Another resident, Sundar Lal, initially mistook the noise for monkeys on the terrace, stating, “At first, we thought there were monkeys on our terrace making noise, but then we realized it was an earthquake, so we all ran outside.” These personal accounts bring out the surprise element of the sound component of the earthquake, which contributed to the shock and terror felt by most.

Seismic Activity in Delhi

Several geological factors influence Delhi’s susceptibility to seismic events:

• Proximity to the Himalayan Seismic Belt: Extensive tectonic activity results from the ongoing collision of the Indian and Eurasian plates. The Himalayan region’s main central thrust (MCT) and Main Boundary Thrust (MBT) caused strong earthquakes that heavily hit Delhi.
• Local Fault Lines: The capital is vulnerable to intra-plate earthquakes because of the important geological features that run under it, including the Delhi-Haridwar Ridge and the Aravalli-Delhi Fault System.
• Soil Composition: Much of Delhi lies on soft alluvial soil, which tends to increase seismic waves and thus make even moderate earthquakes seem stronger.

These factors collectively contribute to the region’s classification under Seismic Zone IV, indicating a high risk of seismic activity.

Scientific Insights

Seismologists have explained the phenomenon further. National Centre for Seismology Director Dr OP Mishra added that the shallow earthquake was the primary reason for the sound being very audible at the time of the quake. According to him, shallow seismic movement can produce high-frequency shakes that are likely to be loud when transmitted along the Earth’s crust to its surface. This supports what the eyewitnesses have been testifying regarding the noise from shaking ground.

Historical Context

Delhi has experienced seismic activity in the past, with several significant earthquakes impacting the area:

• 1720 Delhi Earthquake: Believed to have been a 7.5 magnitude quake, the earthquake caused significant damage within the region.
• 1803 Mathura Earthquake: With a magnitude of around 7.5, its impact was significantly felt in Delhi.
• 2015 Nepal Earthquake: Estimated to have a magnitude of 7.8, this faraway earthquake produced shudders that caused panic across Delhi.
• 2023 Nepal Earthquake: Measuring 6.4 in magnitude, it caused felt tremors in the capital.
• These occurrences highlight Delhi’s seismic risk due to remote tectonic activity and regional geological conditions.
• 1803 Mathura Earthquake: Also of about 7.5 magnitude, its impact was widely experienced in Delhi.
• 2015 Nepal Earthquake: This distant earthquake, which had a magnitude of 7.8, caused aftershocks that terrorized Delhi.
• 2023 Nepal Earthquake: With a magnitude of 6.4, the capital experienced felt earthquakes.

These incidents demonstrate the seismic danger that Delhi faces as a result of area geology and distant tectonic activity.

Preparedness and Safety Measures

Considering the seismic vulnerability of Delhi, citizens and the government must take earthquake preparedness seriously:

• Infrastructure Resilience: Making buildings, particularly high-rise buildings, seismic resistant can reduce damage caused by earthquakes. Seismic-proofing existing buildings is also essential.
• Public Awareness: Public awareness programs can educate people on earthquake safety measures, including “Drop, Cover, and Hold On” methods.
• Emergency Response Plans: Enforcement and periodic revision of emergency response plans can improve coordination before, during, and after earthquakes, lessening casualties and damage.

The efficacy of such preventive measures is illustrated by the earthquake. Although there was little damage, the experience of the people reminds one of how much one should exercise caution and preparation when dealing with natural disasters.

Conclusion

The February 17, 2025, Delhi earthquake, which had a magnitude of 4.0, instilled fear worldwide because it was a compound phenomenon involving ground motion and audibility. Science states that the audible sound during the earthquake was produced by P-waves moving through shallow seismicity and then converting into acoustic sound waves when they reached the Earth’s surface—demythologizing demands understanding how seismic wave travel is related to human psychology.