Rowena Lohman

@rowenalohman.bsky.social

InSAR! 🦇On my radar: Earthquakes, subsidence, land surface properties and change detection. 🏳️‍🌈 🏳️‍⚧️ 💛🤍💜🖤 Personal account

NISAR animation before I leave work. Data from June 28 and July 10 over Australia, where the first date was acquired during a big rainstorm (rain rate from IMERG in green-red colors). Note that the NISAR data is much brighter near the storm on that date than it is on the following, July 10 date.

There is a lot to say about the Nolan Odyssey movie. But one point that I think has not been emphasized enough is: this is a film about living in LA, as Nolan, my erstwhile British compatriot and age mate, has done for years. I gather it’s a strange place.

Twice a year, Hawai'i experiences a strange moment where the sun appears to be exactly overhead & anything that is completely vertical casts no shadow. Let's learn about Lāhainā Noon, subsolar points & 'Kau ka lā i ka lolo', meaning "the sun rests on the brains."

From a Reddit forum, a photo of a can of coconut milk with a blue label, papyrus text and a flip-top, on a sidewalk.  It seems to hover because there's no visible shadow.  The pavement is sort of unevenly colored, with bright spots, and the grass along it is green and lush.

NASA-ISRO SAR (NISAR) satellite imaged Venezuela June 25. NISAR SAR interferometry (InSAR) enabled calculation of surface displacement. Displacements have red tones for east and blue tones for west, with white in middle near-zero over fault rupture. Fault ruptured far to east under ocean. #venezuela

Map of north-central Venezuela with NISAR line-of-sight displacement map shown in false color varying from red to white to blue. Red land moved east (towards satellite) and blue land moved west. InSAR only measures land, so ocean and lakes have no measurements. Background map from Google satellite natural-color images on land and bathymetry in ocean.

Composite plot of the two coseismic interferograms (Sentinel-1, from Copernicus) with the USGS epicenters of the two earthquakes and faults from GEM. The shoreline San Sebastián fault lines up with the fringes in the west and is probably the fault responsible.

Bild

It's taken me a while, but here is my first interferogram of the Venezuela earthquakes from Sentinel-1. It's an ascending track to the west of the epicenter, and the pattern of displacements is consistent with slip on a fault that runs close to and parallel to the coast.

Interferogram of the earthquakes in Venezuela. Shows the western extent of the rupture, and that the earthquake was likely on an E-W striking fault.

Olivia Paschall (Cornell): "Bad" pixels (pixels with high amplitude dispersion) in desert areas show more apparent uplift than "good" pixels. You can get a 2 mm/yr bias in uplift rates! Don't average good pixels with bad! Comparing VV and VH polarization time series can help find the bad pixels!

Maps of InSAR velocities in the Laguna Salada area in Mexico – good pixels show positive range change (subsidence). Bad pixels show uplift! The modal difference is 2 mm/yr of uplift!