Prof. Diego Melgar 🌊
@geosmx
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Associate prof. of geophysics at @uoregon . Director of the Cascadia Region Earthquake Science Center @cascadiaEQs . @unam_mx and @scripps_ocean alumn 🇺🇸🇲🇽
Eugene, OR
Joined January 2011
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Here's our kinematic model for the Türkiye doublet on a 3D geometry from HR-GNSS and strong motion. Penomenal effort by
@TuncayTaymaz
, Athanassios Ganas,
@bwcphd
and many others. This was a fast and furious multinational work with folks in Türkiye, Greece, and the US (1/n)
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Fellow faculty, the simple truth is that the cost of academic labor has been artificially low for ages. We pay poverty wages, there's no getting around that, and so, the cause of the UC strikers is to the benefit of all of us in science. If you are serious about diversity...
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You know what saves lives in an earthquake? It's not quackery and fantasy and earthquake prediction. It's simple: BUILDING CODES save lives. Especially if they are properly enforced
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The 324th birthday of the 1700 magnitude 9 Cascadia earthquake and tsunami. Why is this earthquake so important for the Pacific Northwest?
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Today is the 11th anniversary of the M9 Tohoku-oki earthquake. The ~30m tsunami took 20,000 lives and the earthquake revolutionized our understanding of shallow slip. It happened in the 2nd year of my PhD and is why I'm a tsunami scientist. This is from my thesis work!
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🧵A big earthquake happened 322 yrs ago. We know that from geology, geophysical modeling, and historical accounts of the tsunami that made it across the ocean to Japan. But much remains to be learned. Did it really rupture the entire plate boundary? (1/n)
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Just noticed station TK.3138, only 800 m from the M7.8 rupture. It has ~120%g of acceleration in the vertical! That's unheard of I think. This would mean that, for a moment, you would be, not weightless, but being flung up in the air at ~20%g. If real this is an amazing record
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This is the geometry we're using to reconcile all the observations for both large events in the Türkiye doublet (InSAR, GNSS, strong motion, etc). It really challenges your notion of a "fault" or an "earthquake"!
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Remarkable accelerations reported by
@nied_e
for the M7.5 earthquake. Recall 1g=980gal. A triumph of Japanese science and engineering, because, while extent of damages is still being assessed, they look relatively "modest". Anywhere else ground motions like these are catastrophic
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Tsunami movies in
@googleearth
! We've been working on getting Cascadia simulations from
@clawpack
on there and finally succeeding. Here's a nice M9.1 earthquake
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Here's something non-election related. A simulation of what the January 26th 1700 Cascadia earthquake and tsunami could've looked like. This one is for an M8.8.
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... support them. Better pay is a sine qua non condition for attracting and retaining minoritized people. Yes, if the cost of labor were to rise there would be down stream consequences to the system of science ...
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... such as smaller or even fewer research groups. But none of that affects the moral imperative of paying our talented grads and postdocs what their skills and dedication deserves. It's "orthogonal" to the issue as someone said elsewhere.
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About 65cm of coastal uplift from the M7.7 according to this slip model from joint inversion of GNSS processed by
@bwcphd
and a DART buoy. This is common for EQs in Mexico and very helpful because it makes tsunamis less impactful! Elsewhere in the world subsidence is more common
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A work in progress. Tsunami model for the M7.4 in Mexico last week constrained by InSAR, HR-GNSS and DART buoy data. Beautiful edge waves promoted by the flat shelf make for a long lasting tsunami
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A quick summary of the tsunami so far. Peak of 1m at Manzanillo is big by Mexican tsunami standards and possibly damaging for the port there. I bet a tsunami survey will reveal ~2+m inundation close to the epicenter. Elsewhere it is smaller which is good news, but...
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I'm an ex UC-PhD, 10 yrs ago the salary was barely enough. My family was in bad financial shape then, I considered leaving to find more lucrative employ. I'm currently one of 3(?) latino seismologists in professorial ranks in the US: that's why the trike is also a diversity issue
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The Cascadia Region Earthquake Science Center (CRESCENT) is funded! This is a labor of love and a truly grassroots effort involving well over 50 people in its planning! We will soon open our doors to the community at large, stay tuned for updates!
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How long after an earthquake will the tsunami strike the Cascadia shorelines? Below is a map showing that, relevant after yesterday's NYT article. 10 mins in some places, 50 mins in others. But the devil's in the detail! A thread...
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Earthquake early warning for very large EQs (M7.5+) is tricky. Geodetic data (GNSS specifically) and machine learning can help! Below is an example for the Mw8.8 Maule, Chile EQ from MLARGE v2 an algorithm that estimates Mw and source location/dimensions from real-time data 1/n
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Lots of questions from folks. This is a seismogram from the mag 7.8 event recorded at the station in the green circle on the right. The faults that moved are the colored lines. The wiggles show the shaking was extremely high, anything over 2 m/s/s is considered "very strong" 1/n
Just noticed station TK.3138, only 800 m from the M7.8 rupture. It has ~120%g of acceleration in the vertical! That's unheard of I think. This would mean that, for a moment, you would be, not weightless, but being flung up in the air at ~20%g. If real this is an amazing record
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🌊🌊🌊 Japanese grand master Hokusai's "The Great Wave off Kanagawa" earned him widespread acclaim. These days it is frequently used as part of the iconography of tsunamis, but it most likely was never meant to represent that! 1/n
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This week alone I've received 5 requests for review. Look I've been an AE for 4yrs, I know there's a shortage of reviewers. I know this affects us all. There's an easy fix: PAY PEER REVIEWERS FOR THEIR WORK
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Next day update on the tsunami: Manzanillo took the biggest hit and small waves are still going, all other sites are almost back to background levels. None of the sites are on top of the EQ, so I'd expect a survey will reveal bigger tsunami amplitudes there
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I started baking a few months ago, this is my first attempt at a real cake. Double chocolate with cayenne chocolate buttercream. Also piping is hard...
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@jvhurley
There sure are and I totally forgot to bring that up too. Check out this great write up
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chatGPT is a productivity tool. Here's an example, it would've taken me a bit (20 mins?) to remember how to do this. Instead I got it done right away.
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Playing a little more with
@googleearth
. Here's the same tsunami inundating the northern OR coast. Absolutely catastrophic and horrifying to think about. Inundation distance is 2+ km. By running thousands of models like this we can understand what is likely and how to prepare!
Tsunami movies in
@googleearth
! We've been working on getting Cascadia simulations from
@clawpack
on there and finally succeeding. Here's a nice M9.1 earthquake
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First rough model of the tsunami from today's M7.5 earthquake in Mexico using the USGS finite fault as input. Clear edgewaves and shelf resonance in the Tehuantepec gulf.
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I've seen claims that the directivity is away from Port-au-Prince but the finite fault and the ~25s duration suggests a bilateral event?
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After six years as faculty I finally managed to get a picture of the lab group 🤓
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For one, because when we can't answer the question of how bad future earthquakes will be if we don't understand what past earthquakes have done. So knowing that magnitude 9 events are possible in our region changes everything!
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I ask DALLE2 to make a painting about geophysics in the style of my favorite Mexican artist, Remedios Varo. Nailed it.
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@AlMaXx8017
Al contrario hermano. Los edificos que no se cayeron, los trenes que no se desvielaron, las vidas que no se perdieron, todas son prueba del exito de la sismologia mexicana con la cual se crearon códigos de cosntruccion, mapas de peligros, alertas, y un sin fin de otras cosas
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Also, check out these strong motion and HR-GNSS records close to the epicenter. It's not possible to model the obvious two-stage ground motion without involving multiple structures with delayed slip (we tried!) 3/n
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Got a google alert for my name. A+ quote, 10/10 would do again.
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A subset of thousands of scenario ruptures in the Alaska subduction zone that will be used to test some concepts in probabilistic tsunami hazards analysis. Some of these are scary to think about!
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Ok look
@AGU
does wonderful things, I love it! But it also picks our pockets. Look up the organization financials on
@propublica
, here are the officer salaries in 2015 and in 2019. The expensive AGU meeting is NOT just "inflationary pressures". Oh yeah remember GRL page charges?
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The USGS has been producing teleseismic finite faults for a while now. Over the last 6 months we've been working with
@dara_berg_
and
@accelerogram
to introduce regional GNSS and strong motion into them. Here it is making its debut for the Antelope eq!
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Earthquake early warning for large (M8+) earthquakes is hard. Ph.D student Jiun-ting Lin shows a neat way to use deep learning on GNSS data to quickly characterize them! Read about our test on the Chilean 🇨🇱 network. Thanks as always to
@Sismos_UCHILE
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I have submitted my tenure file, this is the mother of all peer reviews. Now we wait
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📢📢📢 Job alert! 2-year NASA-funded postdoc position in ML, earthquake science, and hazards, using GNSS. We review apps starting January 1st, two page cover letter and CV with references can be submitted at the link below. DM me for details!
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The 1700 EQ helps us understand what tsunami inundation can be next time, like in the model below. This allows us to decide where we should and should not build critical infrastructure like schools and hospitals, or where we need evacuation towers and how tall they ought to be.
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The ~M7.5 event in Mexico ocurred smack in between two tide gauges, Lazaro Cardenas and Manzanillo. In the picture below the changing sea level is the regular tides, the errant dots are outliers (noisy instrument), no tsunami waves are visible yet. Hopefully it stays that way
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Updated finite fault from
@dara_berg_
at the USGS. Now showing unilateral rupture in agreement with InSAR. Seems pretty compact for an M7.2!
#haitiearthquake
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Our first paper submitted to
@WeAreSeismica
is in 🔥🔥🔥 I'm very excited about this, there is another way!
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@HarryBloke
That's how physics works! And it's not a small island chain. The big island rises more than 28,000 ft from the bottom of the ocean to the tip of Mauna Loa, the islands are a HUGE feature
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Funny how AFTER the earthquake all the prediction people suddenly got everything right. Folks, if prediction worked, that person or team would be the proud owner of a Nobel prize and a significant amount of wealth. Don't be tricked by bottom-dwellers!
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1/ This is a "tough but fair" article that discusses the harsh reality of tsunami warning capabilities right now in the US system. We need serious spending on people and technology
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Some time ago we read a paper titled "Quaketomato" about a tomato plant that foretold earthquakes from voltage changes. It became a meme in the group, so we made shirts. Design by
@sydneydybing
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Geophysics fieldwork is fun. I had the fortune of helping out with a node deployment+random sensor work at Mount St. Helens. Here's a panorama video from just below the entrance to the crater rim (1/7)
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Manzanillo had been down since the earthquake origin time, it just reported its first data, currently peaking at 60cm, that's significantly bigger than the other sites and is quite large for Mexico, wouldn't be surprised if 1-2m waves are seen very close to the EQ.
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High-rate GNSS has noise levels in the 2-5 cm range. Can we get it down to mm level? Here we adapted a deep learning denoiser used in broadband seismology for this task and demonstrated it on the Ridgecrest earthquake sequence, it worked pretty well, but there are challenges ...
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Well, I was looking forward to AGU but now I won't be going. It's for a good reason. I have my naturalization interview that week! I just don't trust O'Hare in the winter so I decided to stay here and play it safe. Y'all have fun there
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It's also important because the geologic clues it's left behind are diverse, striking, and widespread throughout the region. 6 ft of coastal subsidence, tsunami deposits miles inland, and so on. It drives home the point for those of us alive today of what the future holds
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(1/2) A tsunami misconception I've recently come across (from a paper review): That tsunami potential energy is a function of the water depth. i.e. if a tsunami occurs in deeper water it is somehow more energetic than if it occurs in shallow water. This isn't so!
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This is not my university and not my fight but it's excruciatingly painful to see a big school like this just blatantly lie. Grads are always hired at 0.49 FTE and forbidden from claiming compensation beyond that, this infographic is made assuming 1.0 FTE and is meant to mislead
.
@UMich
is ready, willing and eager to bargain with GEO over a compensation plan, but it requires movement from both sides. Real bargaining requires real compromise.
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The IOC provides a good way for you to look at the tsunami impacts as recorded by the world's tide gauge network. Keep in mind this includes tides as well as tsunami signals
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(1/n) All science is valuable because “value” is epistemologically subjective. Science has no intrinsic worth except that which we decide to assign it. When discussing this I see people fall into two common thinking traps, especially in the geosciences. Here is a thread.
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@rengin8
I'm not saying the building codes in Turkey are bad. I don't know anything about that. But I suspect Turkey is like Mexico which I know very well, and there, building codes are frequently ignored! I'm also saying we don't need magic, we just need good science and engineering
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Say no to things. A good enough reason is because you are overwhelmed and have too much going on. For some, "too much" might be 3 things, for others 30 things and that's ok. Remember that your mental health is as important as your physical health
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We know how to build tsunami evacuation towers and the technology to issue early warning that gives people enough time to get to safety is in hand as well. If we set our mind to it we can build resilience in the PNW, we are not helpless, we just need to get to work 💪🏽
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USGS finite fault from teleseismic data is up, hints at maybe unilateral rupture towards the northwest. Maybe explains why the tide gauge at Manzanillo (to the NW) is so much bigger than the one at Lazaro Cardenas (to the SE)...
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Come join us at the brand spanking new Cascadia Region Earthquake Science Center and make a difference in how we prepare for earthquakes! We have two job openings, one for Assistant Director and another for Community Collaborations Program Manager. Links in the thread below!
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1/n Whenever there's a big earthquake there's a rush of activity, a furious need to go "work on it". It's the storm chasing version of seismology. It's equal parts stressful and exciting, why do we do it?
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The earthquake seems to be further from Port-au-Prince than in 2020, but, the president was assassinated last month, there's covid, and the hurricane season is warming up. This will be a drawn out humanitarian crisis 😱
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We're getting seismic retrofits on the house today. As a seismologist living on the Cascadia subduction zone I feel a little less like a hypocrite.
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Doing research in a place you don't know? Make sure place names are correct. It matters. There's a paper out in
@SeismoSocietyAm
's TSR on the Coalcoman, MX earthquake. It's well done, I like it! But "Puerto" should be "Puerto Vallarta" and "Lazaro" should be "Lázaro Cárdenas"
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How much longer are we going to ignore that part of the
@theAGU
's bussiness model is the commodification of the scientific endeavor? How is this "community driven" anymore?
Okay this is actually absurd for
@theAGU
registration. Going to be the most expensive way to catch COVID in history.
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