Just an upadte for landslides triggered by the Nepal Earthquake.
The key point is to evaluate the landslides and the potential mass wasting during the coming monsoon.
http://blogs.agu.org/landslideblog/2015/05/06/gorkha-earthquake-landslide-hazard/
This summary, from http://cires1.colorado.edu, describes the previous seismicity an deformation before the Nepal earthquake, for instance some seismicity close the rupture area occurred ~ 24 before the main shock. Thus, this article shows the historical big ones as well as describe zones for future potential big earthquakes along the Himalayas.
http://cires1.colorado.edu/~bilham/2015%20Nepal/Nepal_2015_earthquake.html
Here I posted the InSAR observations from ESA -European Space Agency where they have posted several coseismic interferograms to track the ground deformation on Nepal area.
They compute several interferograms that are available to download. The best interferometric solution, combination of, 17.Apr – 29.Apr (descending), showed around 34 fringes or 1 meter line-of-sight displacement, due the 7.8 earthquake.
http://insarap.org
http://www.bbc.com/news/science-environment-32515059
On the same way, the continuous GPS sites close to the Nepal Earthquake recorded the ground motion. Then, according UNAVCO report, they have compute some seismogeodetic seismograms using GPS data at 1 Hz and and 30 s. The GPS sites are located 200, 400 and ~ 60 km from the earthquake.
http://www.unavco.org/voce/viewtopic.php?f=59&t=1390&sid=e13c8d62c6054d63cfe308aaf5a7c78c#p2507
According the USGS web site, they have analyzed selected P, SH and long-period surface waves to construct a kinematic model of this large earthquake. The NEIC solution (Lon. = 84.7 deg.; Lat. = 28.2 deg., Dep. = 15.0 km), has a fixed depth at 15 km. The fault plane dips 10° and strikes 295° (just north of west). The maximum displacement is ~ 3m (Figure accessed Sunday 26 April, 2015).
http://earthquake.usgs.gov/earthquakes/eventpage/us20002926#scientific_finitefault
![[From the USGS] Cross-section of slip distribution. The strike direction is indicated above each fault plane and the hypocenter location is denoted by a star. Slip amplitude is shown in color and the motion direction of the hanging wall relative to the footwall (rake angle) is indicated with arrows. Contours show the rupture initiation time in seconds.](https://sites.psu.edu/geosc559s2015/wp-content/uploads/sites/21568/2015/04/20002926_slip2.png)
[From the USGS] Cross-section of slip distribution. The strike direction is indicated above each fault plane and the hypocenter location is denoted by a star. Slip amplitude is shown in color and the motion direction of the hanging wall relative to the footwall (rake angle) is indicated with arrows. Contours show the rupture initiation time in seconds.
Recent volcanic eruptions have well documented using seismic, geodetic, infrasound and webcams networks. However, to understand the physical process behind eruptions scientists reproduce some of these process, like lava flows, lahars and most recently ash plumes. Here, I posted an experiment conducted from a scientific team of Universität Würzburg-Germany, Bari University-Italy and the University of Iceland to mimic ash clouds of Eyjafjallajökull 2010 eruption. This experiment allowed scientist calibrate their monitor devices for future eruptions.
https://eos.org/project-updates/fire-in-the-hole-recreating-volcanic-eruptions-with-cannon-blasts
Frontier beneath our feet: Seismic study aims to map Earth’s interior in 3-D
Seismic waves carry information about the Earth’s structure. Thus seismologists combine seismology and computer science to map the Earth’s interior. Here, the Princeton University attempts to map the deep structures on 3D-map. The project will use M>5 worldwide earthquakes recorded on thousands of seismic stations through NSF and research institutions for seismology.
Scientist from Princeton University are interested on map the mantle up welling and plumes, so it will be great make some cross correlations with the Africa rift system currently studied by Andy Nyblade’s group.
http://www.princeton.edu/main/news/archive/S42/59/33Q27/index.xml?section
Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake by Schurr B., et al ., 2014, highlighted the rupture process along a seismic gap in the Iquique region on Chile-South Peru trench. Historic large great earthquakes have occurred in this region and recently international cooperation with Chilenian government has established the Integrated Plate Boundary Observatory Chile (IPOC) to study the northern Chile – South Peru seismic gap.
Great earthquakes (Mw > 8) such as the Arica 1877, Antofagasta 1995 and Arequipa 2001 and several major earthquakes Mw >7 have occurred along the the northern-Chile southern-Peru seismic gap since 19th century. The authors proposed that the total moment accumulated since 1877 from 17 to 25 degrees south latitude is equivalent to a an Mw 9.0 earthquake. Accounting for all events Mw >7 still leaves a seismic moment equivalent of an Mw 8.9 or 8-9 m of slip for the entire gap. Whether a single large earthquake will occur remains unknown, but the potential for a large earthquake in the region remains high.
Scientists use observations as input to construct models to explain the nature, but a model’s value depends on the quality of data and the assumptions behind it. Below is a link to an opinion piece by Edward H. Field of the USGS about models related to earthquakes forecasts for California. The author notes that some models account for segmented fault ruptures while others exclude multi-fault ruptures and that although both use different assumptions, both are useful. The author concludes that we have to quantify relatively which model will be useful under which conditions.
“ Laboratory simulations of fluid/gas induced micro-earthquakes: application to volcano seismology”, Benson et al. , Frontiers in Earth Science, 2014.
Rock failure and pressurized fluids in volcanic systems produce two types of seismic signals, volcano-tectonic and long-period earthquakes. To understand the physics and wave radiation of these processes Benson et al., 2014 tested an analog model. The authors tested physical conditions to generate low frequency seismic signals in a laboratory experiment under known pressure, temperature, and stress and compared it results with volcanic seismic signals where pressure and stresses are unknown.
This paper presents seismograms and frequencies from lab experiments to be compared with seismic data from Mt. Etna and Nisyros volcanoes. They conclude that LP events are more likely triggered by pressure changes in the system via degassing and/or magma movement.
http://journal.frontiersin.org/article/10.3389/feart.2014.00032/full
http://pnsn.org/outreach/earthquakesources/volcanic
This web site describes the mechanism of a Volcano tectonic earthquake (VT), Long Period (LP) and tremor (TR). Seismologists used those terms to characterize the seismic activity of a volcano and made predictions about future activity.
Two examples were recorded before and after the 1980 and 2004 Mount St. Helens eruptions.
http://pnsn.org/volcanoes/mount-st-helens#description-
Although seismicity is the first technique to establish a base line, it important make correlations with the geologic history of a volcano and to combine with geodesy and geochemistry techniques.