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Why All the Earthquakes?

Question: Is the recent spate of earthquakes part of a broader pattern of unusual geological activity?

Arthur Lerner-Lam:  Well they’re unusual in the sense that statistically it’s unusual.  You could say it’s a statistical anomaly, statistical fluke.  There is no reason to think that earthquakes are occurring any more frequently now than they occurred last year or ten years ago or ten years into the future.  There is no reason to believe that, and it has nothing to do with global warming.  Believe me, that’s a question that we often get.

Question: Based on current forecasts, where might we see earthquake activity in the near future?

Arthur Lerner-Lam:  Now, one of the things we learn as seismologists is that earthquakes can occur at any time and any place.  In fact, they don’t even have to occur at plate boundaries for that matter, but that’s a whole other topic, but along some of the major plate boundaries, like the Pacific Northwest,we have evidence of past earthquakes and that actually is an interesting thing.  Obviously we didn’t have instruments going back more than about 100 years or so, so we don’t have an instrumental record, but we have a record from old newspapers for example.  We have a record from some old mission records, particularly in California, Spanish mission records and elsewhere throughout the western hemisphere.  We have very long historical records in China and Japan and in parts of Asia where people have been writing things down for quite a few centuries, but in some places we simply don’t have that written record and we have to rely again on proxies. 

There are a couple of things we can do in a place like California or Seattle.  Let’s take California first.  One thing we can do when we have a fault like the San Andreas is to actually dig a trench across that fault and when we trench across faults like that and you do that trenching at different places; you can actually see in the disturbed soil the record of past earthquakes.  It may occur every 150 or 200 or 3 or 400 years, but with very good carbon dating or other geological techniques we can get a good sense of what that history is and by doing that trenching at various places along the fault we can even get an estimate of the size of the rupture, which gives us a way to calculate the magnitude.  That then allows us to calculate the repeat interval, say, for these very large earthquakes.  In Seattle or actually more generally, off the coast of British Columbia, Washington and Oregon going down into Northern California that’s a different kind of a plate boundary.  It’s what we call a subduction zone.  It’s a convergent boundary.  It creates the Cascades and the volcanoes, so we can’t trench it, but what we can do is look at the history of uplift on the coast because every time and earthquake occurs the upper plate, which is basically the coast of Washington and Oregon and Northern California gets bumped up a little bit and by looking at the sedimentary record, actually sometimes it can go down as well, but you know looking at the sedimentary record, looking at the way say even trees are drowned by encroaching water or lifted above the water table and so on you can get a sense of the history.  People who look at things like tree rings or the history of corals.  There aren’t any corals up there now, but if we go elsewhere around the world we see that.  These are all proxies for past big earthquakes. 

There is another proxy, which and particularly for the Pacific Northwest works, and that is earthquakes along that boundary have a tendency to generate a tsunami and when a tsunami propagates or moves across the Pacific Ocean, particularly a big one, when it hits islands on the other side of the Pacific you get what is called tsunami deposits.  It’s a very turbulent phenomenon.  It brings up pebbles and rocks and disturbs the beaches and you can detect some of those, but and particularly, for the particular case of the Pacific Northwest around 1700, actually in 1700 a tsunami was generated.  It was recorded in Japan and by looking at the tsunami records in Japan, both the historical record and the actual geologic record of the tsunami modelers have been able to kind of back project that, go backwards across the Pacific, show that the source of that tsunami was in fact the Pacific Northwest and get a good date, 1700 for that event.  That event looks like to be about a magnitude 9, 9 ½.  That’s bigger than what we had in Chile just a few weeks ago and it’s about as big as the biggest earthquake we’ve recorded instrumentally.  So now that we know that that boundary can support a monstrous earthquake, a magnitude 9, we can go about the job of measuring how fast the plates are converging, making some assumptions about how stress is building up and come up with some sense of what the repeat interval might be for that earthquake and sad to say we’re pretty close to the repeat interval for that earthquake, so that is a forecast.  It’s not a prediction.  It’s a forecast and thankfully, at least in the United States, going back a decade or more, Seattle and Oregon have been well aware of the potential for that earthquake and they’re taking the appropriate steps one would say to try to mitigate the potential damage.

From Haiti to Chile, China to California, earthquakes have dominated recent news. Is this a pattern or a fluke? And where might the next one hit?

The “new normal” paradox: What COVID-19 has revealed about higher education

Higher education faces challenges that are unlike any other industry. What path will ASU, and universities like ASU, take in a post-COVID world?

Photo: Luis Robayo/AFP via Getty Images
Sponsored by Charles Koch Foundation
  • Everywhere you turn, the idea that coronavirus has brought on a "new normal" is present and true. But for higher education, COVID-19 exposes a long list of pernicious old problems more than it presents new problems.
  • It was widely known, yet ignored, that digital instruction must be embraced. When combined with traditional, in-person teaching, it can enhance student learning outcomes at scale.
  • COVID-19 has forced institutions to understand that far too many higher education outcomes are determined by a student's family income, and in the context of COVID-19 this means that lower-income students, first-generation students and students of color will be disproportionately afflicted.
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What if Middle-earth was in Pakistan?

Iranian Tolkien scholar finds intriguing parallels between subcontinental geography and famous map of Middle-earth.

Image: Mohammad Reza Kamali, reproduced with kind permission
Strange Maps
  • J.R.R. Tolkien hinted that his stories are set in a really ancient version of Europe.
  • But a fantasy realm can be inspired by a variety of places; and perhaps so is Tolkien's world.
  • These intriguing similarities with Asian topography show that it may be time to 'decolonise' Middle-earth.
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Giant whale sharks have teeth on their eyeballs

The ocean's largest shark relies on vision more than previously believed.

Photo by Koichi Kamoshida/Getty Images
Surprising Science
  • Japanese researchers discovered that the whale shark has "tiny teeth"—dermal denticles—protecting its eyes from abrasion.
  • They also found the shark is able to retract its eyeball into the eye socket.
  • Their research confirms that this giant fish relies on vision more than previously believed.
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NASA releases first sounds ever captured on Mars

On Friday, NASA's InSight Mars lander captured and transmitted historic audio from the red planet.

NASA
Surprising Science
  • The audio captured by the lander is of Martian winds blowing at an estimated 10 to 15 mph.
  • It was taken by the InSight Mars lander, which is designed to help scientists learn more about the formation of rocky planets, and possibly discover liquid water on Mars.
  • Microphones are essentially an "extra sense" that scientists can use during experiments on other planets.
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A massive star has mysteriously vanished, confusing astronomers

A gigantic star makes off during an eight-year gap in observations.

Image source: ESO/L. Calçada
Surprising Science
  • The massive star in the Kinsman Dwarf Galaxy seems to have disappeared between 2011 and 2019.
  • It's likely that it erupted, but could it have collapsed into a black hole without a supernova?
  • Maybe it's still there, but much less luminous and/or covered by dust.

A "very massive star" in the Kinman Dwarf galaxy caught the attention of astronomers in the early years of the 2000s: It seemed to be reaching a late-ish chapter in its life story and offered a rare chance to observe the death of a large star in a region low in metallicity. However, by the time scientists had the chance to turn the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Paranal, Chile back around to it in 2019 — it's not a slow-turner, just an in-demand device — it was utterly gone without a trace. But how?

The two leading theories about what happened are that either it's still there, still erupting its way through its death throes, with less luminosity and perhaps obscured by dust, or it just up and collapsed into a black hole without going through a supernova stage. "If true, this would be the first direct detection of such a monster star ending its life in this manner," says Andrew Allan of Trinity College Dublin, Ireland, leader of the observation team whose study is published in Monthly Notices of the Royal Astronomical Society.

So, em...

Between astronomers' last look in 2011 and 2019 is a large enough interval of time for something to happen. Not that 2001 (when it was first observed) or 2019 have much meaning, since we're always watching the past out there and the Kinman Dwarf Galaxy is 75 million light years away. We often think of cosmic events as slow-moving phenomena because so often their follow-on effects are massive and unfold to us over time. But things happen just as fast big as small. The number of things that happened in the first 10 millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang, for example, is insane.

In any event, the Kinsman Dwarf Galaxy, or PHL 293B, is far way, too far for astronomers to directly observe its stars. Their presence can be inferred from spectroscopic signatures — specifically, PHL 293B between 2001 and 2011 consistently featured strong signatures of hydrogen that indicated the presence of a massive "luminous blue variable" (LBV) star about 2.5 times more brilliant than our Sun. Astronomers suspect that some very large stars may spend their final years as LBVs.

Though LBVs are known to experience radical shifts in spectra and brightness, they reliably leave specific traces that help confirm their ongoing presence. In 2019 the hydrogen signatures, and such traces, were gone. Allan says, "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."

The Kinsman Dwarf Galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Explosive, massive, Wolf-Rayet stars are seldom seen in such environments — NASA refers to such stars as those that "live fast, die hard." Red supergiants are also rare to low Z environments. The now-missing star was looked to as a rare opportunity to observe a massive star's late stages in such an environment.

Celestial sleuthing

In August 2019, the team pointed the four eight-meter telescopes of ESO's ESPRESSO array simultaneously toward the LBV's former location: nothing. They also gave the VLT's X-shooter instrument a shot a few months later: also nothing.

Still pursuing the missing star, the scientists acquired access to older data for comparison to what they already felt they knew. "The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009," says Andrea Mehner, an ESO staff member who worked on the study. "The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view."

Examination of this data suggested that the LBV may have indeed been winding up to a grand final sometime after 2011.

Team member Jose Groh, also of Trinity College, says "We may have detected one of the most massive stars of the local Universe going gently into the night. Our discovery would not have been made without using the powerful ESO 8-meter telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO."

Combining the 2019 data with contemporaneous Hubble Space Telescope (HST) imagery leaves the authors of the reports with the sense that "the LBV was in an eruptive state at least between 2001 and 2011, which then ended, and may have been followed by a collapse into a massive BH without the production of an SN. This scenario is consistent with the available HST and ground-based photometry."

Or...

A star collapsing into a black hole without a supernova would be a rare event, and that argues against the idea. The paper also notes that we may simply have missed the star's supernova during the eight-year observation gap.

LBVs are known to be highly unstable, so the star dropping to a state of less luminosity or producing a dust cover would be much more in the realm of expected behavior.

Says the paper: "A combination of a slightly reduced luminosity and a thick dusty shell could result in the star being obscured. While the lack of variability between the 2009 and 2019 near-infrared continuum from our X-shooter spectra eliminates the possibility of formation of hot dust (⪆1500 K), mid-infrared observations are necessary to rule out a slowly expanding cooler dust shell."

The authors of the report are pretty confident the star experienced a dramatic eruption after 2011. Beyond that, though:

"Based on our observations and models, we suggest that PHL 293B hosted an LBV with an eruption that ended sometime after 2011. This could have been followed by
(1) a surviving star or
(2) a collapse of the LBV to a BH [black hole] without the production of a bright SN, but possibly with a weak transient."

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