Research

Mantle Beneath Oceans

I am working on some interesting topics in Marine Seismology. In the past two decades, there has been a revolution in ocean bottom seismology with innovative and cutting-edge technological advancements. However, Ocean seismology is still full of challenges due to high level of noise recorded in the seismograms. With extreme challenges and extensive research scope in marine datasets, my current research focuses on exploring the mantle structure beneath the lowest geoid (The Indian Ocean Geoid Low [IOGL]) on the globe. 

F1. A global geoid map highlighting the major geoid anomalies. The color (in red) indicates positive and (in blue) indicates negative geoid anomalies

     IOGL is a scientific experiment initiated at the National Center for  Polar and Ocean Research, under the aegis of the Ministry of Earth Sciences, to explore the Indian Ocean Geoid Low.

 

(Image source: https://kumoffshore.com/products/nammu/)

Here, I utilize NAMMU model of Ocean Bottom Seismometer (OBS) with a dynamic range of 120s - 100 Hz to record the earth vibrations at the seabed. Seventeen of these little exploring divers (the OBSs) began their journey in May 2018, into the depths of the Indian Ocean. For fourteen long months [May 18 to June 19] they strived to gather the precious information about Earth's interior while sitting at the bottom of the Ocean.

F2. A schematic model to explain the mantle conditions beneath the IOGL region.

For details please refer to Negi et al. (2022) [DOI: 10.1016/j.tecto.2022.229330].

Stochastic Seismic Noise

Can we convert noisy data into a worthy set of information? To address this issue, I worked on designing a tool that reduces the seismic noise from the earthquake dataset. A paper published in Seismological Research Letters, 2021, aims to reduce stochastic noise based on the concept of a data-adaptive polarization algorithm. (For more details please check the publication section)

What OBS data can offer? 

There are various topics that can be explored with the help of ocean seismological dataset (e.g., Ocean noises,  Underwater Hazards (Unheard Volcanic tremors and Landslides), Climatological disturbances (cyclones), Monitoring Marine mammal habitats [whales], etc.,).

Mystery of  Himalayan Earthquakes 

I am always eager to understand the complex behaviour of the tectonically most active mountain chain in the world, the Himalaya. I worked on potential subsurface structures that could generate significant hazardous earthquakes in the Himalaya.
Here is the basic working model to sum up my research in the Himalaya during my Ph.D.

F3. The study area shown inside the blue box highlights the Kumaun and Garhwal Himalaya. The large to great earthquakes along the Himalayan arc are shown by red stars. Local 3-D tomography models for Vp and Vp/Vs anomalies and the interpreted seismotectonic model conclude the zone of moderate and microearthquake zone in northwest Himalaya. (Negi et al., 2017; Thesis, Negi 2017)