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Practice English Speaking&Listening with: Seismicity of the 2018 Kīlauea Volcano eruption

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So in 2018, we got three years

of earthquakes in three months.

That set the stage for what I'm gonna talk about tonight.

So, three years of earthquakes in three months.

What did we learn from that?

What have we observed?

That's what we're here to talk about.

This is some of the damage along Crater Rim Drive

in the national park.

First of all, show of hands, who is a local resident?

And who is a visitor?

Now, okay, so this is mainly for the visitors,

but for all of us, it's a refresher.

Here's the volcano, Kilauea.

There are different regions on the volcano.

The summit, where we are now, is the site

of the 10-year eruption at Halema'uma'u,

which concluded in 2018.

We have the Upper East Rift Zone,

the Middle East Rift Zone,

which is the site of the Pu'u 'O'o eruption,

which was very long-lived from '83 to '18.

What we're here to talk about tonight

is the 2018 eruption down in Leilani,

Lower East Rift Zone, which occurred during the summer

of that year, and the South Flank,

you'll hear me talking about that as well.

When I talk about that, it's this whole area to the south.

So that's the volcano that we're here to talk about,

those are the areas.

I thought I'd start off with where are we right now.

This is a typical week of earthquakes in Hawaii.

And this is what happened last week.

400 something earthquakes on the island.

The ones that are labeled are ones people felt,

or at least reported felt.

And you can see they occur mostly on Kilauea and Mauna Loa,

some scattered around the north part of the island as well.

These are cross-sections in depth,

going north-south and east-west,

if you want to know what it looks like underground.

So that's the typical week, 400 something, 500 earthquakes,

multiply that by four and you get

about 1,500 to 2,000 a month.

So if we go back in time in our earthquake catalog,

all the way back to 1959,

you can see, we're pretty consistent.

There are some ups and downs,

but it's always around that number per month.

But look at this.

What's going on here?

So this was the 2018 eruption.

This is what was so unusual about that eruption.

It's never been, that amount of earthquakes

has never been measured before in Hawaii,

20 times higher than the normal rate.

And another thing, I'll zoom in on that a little bit,

so here we are.

Here's that eruption.

Remember I said it was three years

of earthquakes in three months?

Here they are, May, June and July mostly,

also August right there.

One thing to note, is that the level

of earthquake activity right now,

as measured by the counts, this is again, per month,

is it got twice as much as it was before the eruption.

So, the volcano is still settling, it's still adjusting,

and that's producing earthquakes still to this day.

So there are some questions I want to pose,

and hopefully we'll answer by the end of the talk.

Why is that plot there?

Why is that seismicity rate so high?

That's one of the questions.

What kind of processes made it so high?

So we'll try to answer that.

And why is it still elevated today,

which I alluded to already?

So if we plot the earthquakes on a map from the eruption,

this is just the ones during the first few weeks,

magnitude 2.7 and higher.

You can see this interesting pattern here,

which we'll get to a little bit later.

There are three main sequences,

or groupings, of these earthquakes.

The first one, the Lower East Rift Zone, or LERZ grouping

occurred down here during the first two weeks

or so of the eruption.

You can see earthquakes per week plotted,

and you can see mostly these three weeks

is when the story was going on right there,

and we'll talk about why in a minute, it tailed off.

The second topic is the South Flank.

This is this large area.

If you recall that rectangle I put up there before,

but it also extends offshore quite a ways.

And you can see earthquakes showing up out there as well,

related to the 6.9 earthquake.

And finally, really the big story,

is the summit with all of these earthquakes shown in blue,

almost 50,000, depending on how you count them,

at the summit during the eruption.

So we'll start off with the Lower East Rift first.

Here's an example of the lava covering one

of the roads in Leilani Estates.

So what was happening before that eruption?

This shows the two months before the eruption,

and I'll explain what's going on here.

So here's the summit, here's the caldera,

here we are up here.

Throughout March and April,

swarms of earthquakes were happening.

These are groupings of earthquakes close together

in space and time.

Each time you see one of these,

some of them are noted by these purple bars,

was a swarm of earthquakes.

And what was happening at the time?

The volcano was engorged with lava,

we were seeing inflation at the summit,

inflation at Pu'u 'O'o,

the lava lake overflowed in late April.

And in fact, when that happened,

there was a very, very productive swarm of earthquakes,

these shallow orange ones right here

in the Upper East Rift Zone connector,

that little sliver on my earlier map.

That really heralded a big change that was about to happen.

We didn't know what was about to happen,

but on April 30th, it happened.

And that was the collapse of Pu'u 'O'o.

This was what the view looked like,

similar to what the view looked like, from HVO on that day.

You could see a pink-looking plume rise up

from the edifice of Pu'u 'O'o.

Later it was verified that, yes,

the lava lake was there had drained away.

And this used to be full of lava.

Where did it go?

Well, it went down to the East Rift Zone,

and this is the simple view of it.

So it was here, it drained down and went that way.

As it did that, it produced a lot of earthquakes.

So this is an example of one day's worth

of earthquakes observed at one station

in the Middle East Rift Zone, known as JOKA.

May 2nd, it turns out this is the day

before the eruption began.

This is an example of a swarm,

a lot of earthquakes close together in time.

And the idea here, if you look at this cartoon,

is that there is a finger or a blade of magma underground.

You can think of it, it's called a dike,

and it's pushing its way through cracks

and it's forcing its way to make bigger cracks

to open up new space.

And each time it does that, it makes an earthquake.

Earthquakes happen when rock breaks.

And so that's happening right at that tip,

right at the front, and basically,

we can map out where the front of that dike is

as it moves, and that's we were doing.

However, we knew it was going down

to the Lower East Rift Zone, where, it turns out,

we really didn't have a lot of coverage of our stations

to monitor that region.

We only had two stations there

before the eruption, these two.

So we scrambled, and went out there

the first week and put in more.

And this is one of the ones that I helped install.

We dig a hole, we put the instrument in the ground.

And you can see, so we started off with that,

then we put in all of these,

and we had some help with some of these.

But we had a pretty good network after that,

in order to accurately locate

and characterize the earthquakes.

Then the lava came and took out four of those, ultimately.

But while they were there, they provided very important data

to us, and we actually rescued the equipment

at two of those sites right before the lava got them.

And so from that, we had a good catalog of earthquakes

that helped characterize where that dike was

at any given time, and of course,

if there were going to be changes in the eruption.

So this is a video put together by our colleagues

over at PTWC using our data.

So that's one of the swarms that happened in mid-April

that I talked about earlier under the summit.

You can see these were going on,

keeping us quite busy, I should say,

even before the eruption started.

These are the ones in that Upper East Rift connector

that really were right before the eruption began,

before Pu'u 'O'o collapsed.

And here we go, there it is.

And there they go, did you notice them moving east?

(audience gasping)

That's the 6.9 earthquake,

which we'll talk about in a minute too.

But this is the beginning of the eruption

and what the earthquakes were doing,

and just notice how they moved east,

they kind of stopped here,

and they went more east in two pulses.

So one thing that's really interesting,

one of the interesting science results

that's come out of this, based on geochemistry,

is that there were different phases to the eruption.

So the first lava that came out

was thick and viscous and sticky.

We interpret that as being older.

And then, later, once that was flushed out,

fresher, hotter, more fluid magma came out.

We actually see it seismically with earthquakes,

this change, as well.

So this plot is, I'll explain it here.

So this is showing the progression of earthquakes

from Pu'u 'O'o in the west, down here,

all the way to Leilani in the east, up here.

So, it's southwest, northeast.

If you look at the slope of this,

so this is distance versus time here,

so you can't quite see, it's cut off,

but this is May 1st, May 2nd, May 3rd.

So, over a period of about two days,

it travels some 20 kilometers or so.

This is about the speed you could walk,

just a comfortable walking pace.

So now we know how fast that dike

was moving underground just by plotting this up.

But notice how this line is pretty steep

and then it rolled over and got flat?

That's because the dike decided to stop where it was.

It stayed right there in this spot,

which happens to be right there,

under the neighborhood Leilani and surrounding area.

And then on May 3rd, that's when the eruption began.

So this is one of the tools, or pieces of information,

a tool of seismology helped us learn.

And even, we saw a little bit of the shallowing

of earthquakes right before the eruption,

where they started off a little bit deeper,

they got a little bit shallower as it came to the surface.

The next part of that for about,

I'm sorry that this is cut off,

this is from May 4th to May 9th here in this part,

no movement in terms of east or west movement.

The earthquakes just stayed where they were.

They were happy to be right there.

They were parked there.

All the early fissures were opening up.

But notice this.

So right there, on May 10th,

it pushed its way eastward more.

This was that next phase of the eruption beginning,

and it's just really interesting.

Again, just notice this really nice curve.

So the earthquakes were down here

at this depth, three kilometers.

They pushed up to the surface at zero there

and that's when they moved eastward.

Putting it all together, remember I had pointed out earlier

that the first part of this eruption, the first sequence,

really was about two or three weeks long.

And here is the main story there.

There was that first pulse I told you about,

it settled down for around a week,

it made that second advance

that we just talked about on the previous slide,

it settled down and stayed there for the rest of the time,

so it didn't go more east.

At the time, we didn't know.

It might, it could have, but it didn't.

So these are those two general areas of those two eruptions.

So and you can make some interpretations about that as well.

So the end of the story is that seismically,

we saw a first pulse of earthquakes,

this first phase correlated with the geochemistry,

followed by a brief pause in seismicity,

or a relative pause.

The second phase came up next.

This is when it pushed eastward more,

and the magma eventually got hotter.

Fissure 8 took over toward the end of this,

and the rest is history.

Now, one thing that's really interesting is

that right about May 18th, the seismicity rate drops off.

That's about the time that fissure 8 is gonna take over.

The path has been cut, is the interpretation.

The conduit is open.

The rocks don't need to be broken anymore.

So, the earthquakes die down,

but the tremor doesn't die down.

So if you recall this cartoon from earlier,

at the front of that dike

was where the earthquakes are happening.

But behind it, in that conduit,

the magma is resonating and sloshing around,

and this creates this tremor phenomenon,

which is a lower frequency kind of hum

that occurs, which we can also track.

Here's a map showing tremor.

And one of the science results from that,

which Matt Patrick talked about here a couple of weeks ago,

was we could correlate that tremor to changes

in the lava coming out at fissure 8,

the lava level, as well as the lava effusion rate,

how fast it moves.

Also, the temperature has been correlated with it.

So each time, look at this plot.

Each time this goes up and down,

the lava level goes up and down, so they match pretty well.

That's one of the interesting results from that.

So that was the first sequence of the eruption,

and it kept us very busy for the first half

to the first 2/3 of May.

And right in the middle of that

was the magnitude 6.9 earthquake on May 4th.

Who felt that in this room?

Okay, I don't have to tell you about it then.

So this was the shaking pattern,

the ShakeMap, from that earthquake, right here.

This is another view of that same information, the ShakeMap.

So you can see it was most intense down

in the Kalapana area, lower Puna,

and less so the more up the chain you go, up the island.

And so the earthquake occurred here.

You saw this earlier, where those aftershocks

made this circular pattern offshore.

The interpretation of that is that this fault area,

this really low-angle, almost horizontal fault

between the oceanic plate below

and the volcanic material above is what was ruptured.

Basically, this whole thing was mobile,

producing earthquakes, and still is

to a certain degree today.

And we know that the earthquake occurred here

on this part of the fault versus, say,

up here where the fault is steeper,

because with our seismic data,

we can look at the way the seismic waves radiate out.

And we can tell that it was a very low-angle,

almost horizontal fault from that information.

That's what this shows.

We call those beach balls,

because they look like beach balls.

But that's one of the reasons we know this occurred

along that fault, which, the biggest earthquakes

in Hawaii all occur along this fault.

So why did this happen?

Why did this happen?

Well, the eruption, in short, is why it happened.

So when the magma was withdrawn

from the upper part of the East Rift Zone,

and the middle part, it went to the Lower East Rift Zone

that we talked about.

And when it did that, it had to wedge its way in,

and when it forced its way in,

it put sideways pressure on the rock.

What this is showing is a net loss of material here

in the Middle East Rift Zone and a net gain of material

down in the Lower East Rift Zone

from one of the models that's come out of this.

Another view of that, a sideways view,

if you could just slice into the volcano,

as that magma was going in, it was pushing sideways.

And that pushed the whole South Flank to the south.

It might have been ready to go anyway,

but this was the push it needed to get started,

and it moved along that almost horizontal fault down there.

Seismologists have taken this data, as well as GPS data,

even tsunami data and other data,

and they've created models of how the fault ruptured.

These are just two examples from the literature.

All the hot colors, the red, orange, yellow,

show where most of the motion occurred along that surface.

So it starts off here, but it kind of twists around

and moves in these two lobes, here and here,

which is the interpretation right now,

based on the available data.

Some seismologists are arguing

about the magnitude, by the way.

We still think 6.9 is the best representation,

but some people taking in other data think it's 7.2.

These things sometimes change with further interpretation.

We don't know if that will happen,

but with the 1975 earthquake, it started off as a 7.2

and now we think it's a 7.7, for example.

So, it's not unprecedented to think that.

So this earthquake was felt statewide,

more than 500 kilometers away,

all the way up on Oahu and even on Kauai.

Was there damage?

Anybody have damage?

A little bit, yeah?

From this earthquake?

And so the answer is yes,

but no one was talking about it, and for good reason.

(audience laughing)

This was happening.

Actually this part, fissure 8 hadn't happened yet,

but there was an eruption going on.

People were evacuating their homes at this time.

It was a very high intensity crisis going on.

This is one of the news articles

about the earthquake mentioning a power outage,

mentioning some of its effects.

And I thought I'd share a couple of photos

of its effects that I was able to find.

For example, this rock slide

or landslide happened off Chain of Craters Road

near the end of the road, so that happened.

A collapse at Pu'u 'O'o was triggered,

one of many, but this one was ascribed

to the earthquake that day.

And you can see that pinkish color I mentioned earlier.

These cracks in Leilani were reported

by the residents as being due to the earthquake,

so these supposedly opened up at the time

of the earthquake, which is pretty interesting, as well.

There was a tsunami, as well, that I mentioned.

The tsunami was observed statewide.

It was 40 centimeters in Kapoho,

about 30 centimeters in Hilo,

all the way to about five centimeters in Kauai.

This is an example of some of those stations.

And here's the radiation pattern for it.

I thought I'd play this for a minute.

This is in Hilo.

Yeah, I felt the shake.

I was driving in my car.

I felt like three earthquakes.

Right here, the water coming back in.

This is Four Mile Beach.

Water rushing back in.

This island will be covered

in a matter of, a matter of, maybe like one minute now.

It is water, you hear 'em.

(water rushing)

I don't know whether it's a tsunami.

I think it's just aftershocks.

I'll stop it there, aftershocks.

But if you watch the whole video,

you see that island get covered and then exposed again

over a period of five minutes or so.

It's pretty interesting.

And so 30 centimeters, about a foot or so,

going up and down.

So the aftershocks were very plentiful

and are continuing to this day, to a certain degree.

You can see just by eye,

these are all the larger ones, magnitude 2.7 and higher,

that occurred during the first month

or two after the earthquake.

Again, there's that elliptical area

that you can see quite clearly.

This is interpreted as the toe of that area

of the fault that's pushing its way seaward along

that boundary between the two materials under the ocean.

Let's see, what else can we say about it?

It spans about 435 miles.

Now, one of the other models of slip is shown here,

which also agrees roughly

with where the earthquakes occurred.

We think there was about five meters of movement

of the flank of the volcano

just during the earthquake alone.

Okay, so more about those aftershocks.

The 6.9, of course, was the main shock

of the sequence, of the series.

But you don't know that when a sequence begins.

So, the sequence, we can actually trace it back

about two days to May 3rd, a day earlier let's say.

There was a 5.1, which at the time, felt quite big.

And then the next day, there was a 5.7,

which felt even bigger.

I was driving in my car, and it shook the car so violently,

that I knew something was going on.

Janet was with me, actually.

We were about to fly in a helicopter

to go check out Pu'u 'O'o, which had just collapsed.

And I said, "I'm going back to analyze this.

"I better go check this out."

And an hour later, the 6.9 happened.

So, it became the main shock.

That was relegated to be a foreshock.

A number of other ones happened after,

in the magnitude 4 range.

This orange line, by the way,

this curved pattern, is a telltale pattern

of aftershock decay.

It shows how the energy is trying to equilibrate,

trying to spread out and go back to normal over time.

Seismologists can use that information

to help forecast when other aftershocks might happen.

Speaking of which, some USGS seismologists

have used the magnitude 6.9 earthquake and its aftershocks,

as well as historical earthquakes,

to calibrate a new product that'll be coming out very soon,

called the aftershock forecast product.

It's already in use around other regions of the country.

It was very helpful during the Alaska earthquake

that happened a couple of years ago, for example.

This shows just how well their model fits the data,

that's what this is showing, and it's a pretty good fit.

Stay tuned for that.

This is just the summary of that sequence.

You had the 6.9, the decay down,

just kind of a nice decay down,

and then, but remember I told you

that the activity is elevated now

compared to what it was before.

See how before we were getting maybe 100 earthquakes

per week, and now we're getting

about 200 earthquakes per week.

That's because that south flank of the volcano

is still very mobile compared to what it was before.

It's still wanting to slide.

It's still settling, and it's producing more earthquakes

than it would otherwise.

Now on to the third sequence of the eruption, the summit.

This is an example of one of the ash plumes

that came out in the early part of May.

Here's the Jaggar Overlook,

and a very impressive series of events that went on there.

Here's a time lapse.

You may have seen this, but it never gets old.

It's one image per day.

(audience chattering)

Tens of thousands of earthquakes happened

to allow those faults to move

and allow that deformation to take place.

It's just remarkable.

Here was the caldera before,

nice circular crater.

There's the parking lot.

And here it is after.

So it's enlarged quite a bit.

There are different areas,

there's different down-dropped areas.

There's a pit.

Now there's water in this pit.

We've heard about that at a different talk,

and the parking lot has fallen in,

as well as part of the road.

So what were the earthquakes doing?

If you'll recall from the earlier slide,

there were a lot of earthquakes in the summit,

some 40, 50,000, at least, measured during the event.

These were characterized by a cycle.

Basically, this is showing earthquakes per hour.

All these, so earthquakes per hour,

picked up in the magnitude 6.9,

settled down for a little while

and then starting on May 17th,

one of these plumes happened.

And with that was this blip on the tilt record,

where it kind of raised up and then dropped back down.

We didn't know exactly what it was at the time.

We knew it was some kind of explosion,

and this happened again and again and again.

But one interesting thing happened is

at first, they were kind of small,

in terms of energy release

and in terms of numbers of earthquakes, relatively speaking,

to what happened later.

Then things really started to pick up.

So there's a story to this, that we've tried to tease out

in the year and 1/2 that's happened since then.

But this cycle happened 62 times,

and it peaked at about, what's this say?

About 150 earthquakes an hour.

That's 5,000 a day, or so.

I know most of you felt them up here,

(audience laughing)

and you probably are glad they're over.

And also, quite surprising, it stopped very abruptly.

So, the 63rd cycle was partway through,

and it stopped before the collapse happened.

So for some reason, that last one didn't happen.

We interpret these as stepwise collapses,

as the magma is draining away,

the caldera just slowly falls,

well, slowly in between,

and then abruptly falls during the collapse.

Okay, so this is what that is showing

is basically, if a collapse just happened,

it's happy, it's resting on the magma below.

There's no gap there, and everything's good.

So this is showing the earthquake rate being low.

Over time, though, the magma is draining away.

It's like pulling the plug on a bathtub.

Now that floor of this part of the caldera

is no longer supported.

There's a void underneath it, at least a partial void.

These wiggles show that earthquakes are happening to help

because the faults are getting stressed

to try to hold this up.

But the strength of the rock is only so much.

Eventually they give,

and this is, a big collapse happens.

It falls down, so this is lower than this, see?

Now the caldera is at a lower spot.

And then it's stable for a few hours

and then it happens again.

So this is a day's worth of earthquakes

at one of our stations.

If you watch the data on our website,

you would see a similar kind of plot.

You can see lots of earthquake swarm right there

and then it collapses, it's happy,

it's quiet for several hours, maybe you get some sleep.

No more shaking.

It picks up again.

This is roughly a day.

I'll show you in a minute how that varied.

And then it goes again.

So one of the really interesting observations from this

is that, with these tens of thousands of earthquakes,

there really were only a few dozen that were unique.

By that, I mean we've seen repeating earthquakes

where you can compare the shaking pattern of one earthquake

with the shaking pattern of another earthquake

on two different seismograms.

These are different earthquakes.

They actually had almost the exact same shaking.

The interpretation is that it's really

the same fault moving, just a repeat

of what happened before.

What this is showing, each, by the way,

these orange lines are the 62 collapses

through time, from May to August.

All the red bars are the little families

or clusters of these earthquakes that were similar.

There was a family that started here,

it picked up for a while, it went off,

it started again and went off.

It went for several days, maybe a week,

before this other one took over, and this other one.

And so you can see some of these last a week,

some of these last a month, but they don't last forever.

It's just a really interesting observation.

We can also look at that same information

in a depth profile.

Now the colors show each of the different families.

So this red color shows, well,

that cluster or family only occurred at this depth,

maybe half a kilometer depth.

This purple one was right at one kilometer depth.

These are those repeating earthquakes.

They're repeating, because it's the same fault structure

failing the same way over and over again,

until the geometry of the crater changes so much,

that it can't happen anymore.

And so we see it's jumbled in here

because there's a lot going on

during that part of the collapse.

And so that's one of the interesting results

that's come out of this.

And this is that same data,

this is those same colors, in fact,

showing after you carefully relocate all those earthquakes,

most of them, actually, if you look on our website,

it'll look like a buckshot on the caldera.

But when you carefully relocate them,

they mostly actually occur along that boundary,

where the down-drop area happened.

By the way, this little animation is showing with time

how they bounced around different areas of the caldera.

So earlier on, they were in the west,

later they were in the east,

is roughly what we see.

And so the idea, interpretation there again

is that this piston, or this block,

once it was formed, it kind of slipped some in the west

and then it wiggled and slipped more in the east

and then eventually slipped even more in the east.

And that's, I'll have a cartoon

in a minute that'll show that.

Now, when every collapse happened,

you guys may know, that they didn't feel

like normal earthquakes, right?

They felt like you were on a ship,

like you were kind of rocking like this.

Anybody remember that?

Well, I was at a Cooper Center once and that happened,

and everyone cheered.

They thought it was really fun, I guess.

(audience laughing)

Better there than in the park, where it was stronger.

So what this is showing is during,

by the way, each one of these lines

is one of those 62 collapse events.

So this is May, this is August.

I put a square on these because don't these look

a little different than those?

Those first ones were really, really long-period, as we say.

They didn't have much of the jolt

or the high frequency shaking.

In fact, some people couldn't even feel them.

They were very subtle.

In fact, that comes out when,

we can actually compute different kinds of magnitudes.

There's not only one magnitude, there are different kinds.

So if we compare a long-period magnitude

to a short-period at high frequencies, low frequencies,

all those plot down here.

So, they are like this.

They're self-similar.

They're scattered, but they're all in this range.

And what's interesting is,

all the other ones that happened,

starting from May 29th onward, are all up here.

Much tightly clustered by the way.

So two different processes are going on

with these types of earthquakes.

By the way, those later ones, from May 29th on,

were the ones people felt a lot more strongly and widely.

These are the 5.3s that everybody talks about.

These were 4.7s.

Still big, but lacking in high frequencies,

and therefore didn't cause a whole lot of damage.

So that was one observation.

Now, if you look carefully,

you can notice other stages in there as well,

which we think are related to the rotation

of this piston block as it goes down.

Now, another just first-hand observation of the data is,

if this is energy, okay, so a moment is a fancy word

for energy that we use.

Notice how all those first events,

this is from May 17th to 29th,

those first 10 events were right here,

really low energy release.

But something happened on May 29th.

It shot up, and the next several events were up here.

It went back down.

Then it sort of settled out and all the rest were more

or less the same, out here.

There's basically three phases going on.

So there's that first one,

which is those really low-frequency ones

that only some people could feel.

There were these second ones,

which we think is when this, what's called a ring fault,

this circular or semi-circular fault

around the caldera, was actually forming.

And then this last one.

It's formed already.

It's sliding down episodically.

The lower plot, by the way,

is the time between each collapse,

time between the collapses.

So in the beginning, it was kind of scattered,

but mostly low, so 10 to 40 hours, a pretty big range,

but lower than this.

So basically, when that ring fault was forming,

it took longer between events.

Why is that?

My idea is that it's breaking more rock.

It's having to do more work,

and so it takes longer to fail during this time,

up to 60-something hours, in between events.

Once that had happened, a nice surface has been formed.

It can slide along that.

It came into this nice steady pattern

of about 30 hours between events,

which crept up over time, but was pretty consistent.

Why was it so consistent?

I think the interpretation is just

that the magma was draining out very consistently.

This is controlled primarily

by how fast the magma is going away.

So this is that in a nutshell.

In the beginning there was a lava lake.

It drained away.

Once it had all drained away,

we started to see collapses

as the actual magma chamber itself started to drain away.

The vent where the lava lake had been was still open.

That's why the plumes were getting out.

Each time a collapse happened,

it would kick up a lot of material and it would get out.

But that got blocked at some point,

and once it was blocked, really,

there were no more plumes happening.

But it was still collapsing.

The ring fault had formed, mostly in the west,

it formed earlier.

And in the east, it seemed to grow over time.

That's how we see it in cartoon form.

What did it do?

What were the effects?

This is just a selection.

The park was closed, right, we're glad it's open again,

but the park was closed for a long time.

Each time a collapse happened, the scene was like this.

If you were at Tina's talk the first week,

she showed a video of this.

Later, I have a video that you can hear it,

what it sounded like.

I like this one 'cause who knows what that is?

(audience shouting) HVO.

It's HVO.

So poor HVO building up there getting battered.

Now, here's that video, which shows the effects

of shaking at HVO from two different vantage points.

(earth rumbling)

(ground squeaking)

(ground cracking)

Now listen, that's not wind.

You can see the dust.

It's rising.

The dust would just fill the scene

and it would take a while to settle out.

Every 30 hours or so that would happen.

Cars would bounce, cars in that parking lot there,

they would bounce several inches.

Obviously, it created cracks, it created damage.

There's what the sign looks like today.

Inside, it knocked things over.

There are some bookcases.

(audience laughing)

And some more.

You can guess whose offices these are, if you want.

It caused damage to some trails, many trails.

This is just one, one with lesser damage actually.

But thankfully, many of the trails have reopened now.

Buckling in the road, from minor buckling like this,

it shows that there was compression here,

to major buckling like this.

This is a down-drop of 20 feet, maybe.

Taller than you, taller than a car, certainly not drivable.

This is what the scene is like all around

the west side of Crater Rim Drive right now.

Sinkholes.

This one was in front of the Golf Course,

but there are sink holes in the park, too.

That's why Kilauea Overlook is still closed.

There's one of these right in the entrance to it.

And of course, what was it doing,

all that work it was doing?

It was creating this, all these steps going down,

this is where the lake is today.

The parking lot used to be, I think, somewhere here.

But it's just remarkable how much it changed,

and how many earthquakes it took to allow that change.

I like this shot 'cause you can see that eastward fault,

which was just eating away at the old floor as it went.

If this had continued longer,

it probably would have gone more east and more north,

which is off this part of the scene.

It exposed lots of new areas that had never been seen.

This area here, for example.

I think the geologists are gonna have fun

mapping these in the future.

So that was the summit sequence, in a nutshell.

And what happened after the eruption?

It had a small little postscript there.

This was in September, the last little gasp from fissure 8.

What's been going on since then?

Well, we've had inflation, both in the East Rift Zone

and at the summit, which is ongoing.

This is the past year or so.

We know magma is coming back.

This is showing radar images, by the way, from space.

It's one of the ways we can monitor this.

Earthquakes.

So we have lots of earthquakes still occurring,

but in the usual places, at the summit of Kilauea,

the summit of Mauna Loa,

the South Flank that I've talked about,

and this area, the deep Pahala zone,

the deep lower southwest rift, as it's known.

I show this plot down here.

This is showing the last week of the eruption,

when some 2,500 earthquakes happened, compared to now.

So all the variation we've had in the year and 1/2

since then has been pretty consistent compared to then.

So, steady as she goes is what's happening now.

The volcano is adjusting to its new normal,

but it's not changing very rapidly, necessarily.

It's reached a new normal for now.

In summary, there were three sequences with this eruption.

There was the Lower East Rift sequence

associated with the intrusion of that magma

and the opening of the fissures and the different phases

of the opening of those fissures.

There was the South Flank sequence dominated

by the 6.9 earthquake, and that whole zone

of the South Flank slipping

on this almost horizontal fault beneath the island,

and even extending far offshore.

And in the summit sequence,

where the caldera was enlarging itself and becoming deeper

and becoming what you can go see today,

creating unprecedented levels

of seismicity never before measured here,

20 times higher rate than normal.

Three years of earthquakes in three months.

So what about our questions?

So why was the seismicity rate so high?

Well, there was an eruption.

It was the biggest eruption in 200 years,

and this eruption involved both the summit and the flank.

A lot was going on that made a lot of earthquakes.

That's the simple answer.

What type of processes contributed to that high rate?

Well, the three we talked about,

that migration of magma cutting its way down

to the Lower East Rift Zone,

the 6.9 earthquake, and, of course, the caldera collapse.

And finally, why is the rate still a little bit higher now?

It's because the volcano is still pretty mobile.

The South Flank is still moving at a higher rate than usual.

There are still aftershocks happening along that fault,

and there will be for quite some time.

So thank you very much for your attention.

I want to thank everyone who's helped with this.

There are many seismologists and technicians,

and people who have helped keep up with this data,

and we'll be digging out of it for several years.

Especially thanks to Janet for helping put this together.

Mahalo. (audience applauding)

The Description of Seismicity of the 2018 Kīlauea Volcano eruption