Special Event: Nepal

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April 25, 2015 M7.8 earthquake in Nepal

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The April 25, 2015 M 7.8 Nepal earthquake occurred as the result of thrust faulting on or near the main frontal thrust between the subducting India plate and the overriding Eurasia plate to the north. This page is meant to be a collection of preliminary information, results & visualizations for the seismology research community.

Event parameters (from USGS)

Please check the USGS page for the latest official information.

Magnitude 7.8
UTC Time Saturday, April 25, 2015 at 06:11:26 UTC
Location 28.147°N, 84.708°W
Depth 15km (9 miles)
Region ESE of Lamjung, Nepal
Distances 34km (21mi) ESE of Lamjung, Nepal
58km (36mi) NNE of Bharatpur, Nepal
73km (45mi) E of Pokhara, Nepal
76km (47mi) NW of Kirtipur, Nepal
77km (48mi) NW of Kathmandu, Nepal

USGS summary page

Background & some preliminary figures

IRIS EPO Teachable Moments

IRIS Data Products

GeoGateway inversion of GPS data provided by Jean-.-Philippe Avouac (California Institute of Technology and University of Cambridge) and ARIA data analysis using GIPSY-OASIS software and JPL Rapid & Final orbits fits the GPS vectors well with a single fault model. The modeled interferogram in the image is for C-band, Right-looking, Heading 168° spacecraft.
Fault parameter solution:
Epicenter (lat) 28.147°
Epicenter (lon) 84.708°
NE fault corner from epicenter X = 121±9 km
Y = -25±1 km
Strike -75°±1 km
Dip 1.9°±0.5 km
Depth (bottom) 9±0.3 km
Width (up dip) 35±0.3 km
Length 130±9 km
Strike-slip (r.l.) -7±4 cm
Dip-slip (thrust) 531±.2 cm

Andrea Donnellan (JPL)

Strain magnitude map (top) and tilt/slope change map (bottom) based on GeoGateway inversion of GPS data provided by Jean-Philippe Avouac (California Institute of Technology and University of Cambridge) and ARIA data analysis using GIPSY-OASIS software and JPL Rapid & Final orbits. The strain magnitude map highlights areas where the model predicts the greatest ground deformation (motion) has occurred. The tilt/slope change map highlights the areas where the model predicts the greatest vertical deformation and the arrows indicate the direction of the slope change. These maps provide an early estimate of where the deformation has occurred, and where damage may be localized. (Margaret Glasscoe, JPL)

ESA Sentinel-1 satellite interferogram. The interferogram is copyrighted: Copernicus data (2015)/ESA/PPO.labs-Norut-COMET-SEOM Insarap study. (image annotated by Steve Hicks, U Liverpool)

The Ohio State University and the Polar Geospatial Center have released a pre-event 8m posting elevation model for the Kathmandu area. It is produced from DigitalGlobe stereo imagery provided by the National Geospatial-Intellegence Agency under the NextView license. The DEM can be freely distributed. Please see this document for user advise.
Download the DEM

A seissound animation with speed-up sound of seismic data of the magnitude 7.8 Nepal earthquake sequence recorded at station IC.LSA that are about 650 km away. The mainshock trace was clipped, and numerous aftershocks and likely triggered earthquakes could be heard throughout the entire ~4 hour recording. (Zhigang Peng, Georgia Tech)

Additional backprojections

Additional IRIS backprojection movie made using a virtual array centered around Japan. (Alex Hutko, IRIS DMC)

Summary figure for the additional IRIS backprojection using a virtual array centered around Japan. See the backprojection detail page for more details.
One can see coherent energy extending out to ~170km to the east at around 70 s, though the rupture that late is likely very weak. Between about 20-45 s, one can see rapid movement of the energy being imaged. This is consistent with an overall average rupture velocity of ~2km/s with some portions being significantly faster where significant moment was released. See the other IRIS backprojections here

Summary MUSIC backprojection results using a North American array. These results suggest an overall average rupture velocity of ~2km/s consistent with the IRIS backprojections. (Lingsen Meng, UCLA)
Full resolution version of Meng backprojection

NSF SAGE Facility Event Page

The NSF SAGE Facility event page for this event contains links to additional tools and data.


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