Finally a sunny day in Le Marche as work continues apace on the ground floor columns.
Yesterday they started erecting the steel rebar frameworks of the columns and began building the forms around these frameworks for the concrete to be poured. Today saw this project nearing completion.
We got some good pictures today, and one in particular caught my eye. It’s a closeup of the base of the steel rebar framework of one of the columns. You can see how solidly built the columns will be, given this framework will be encased in concrete. This is an example of the construction practices they are using to strengthen the house against earthquakes.
Once they had erected the columns and put the forms around them, we had an impressive grid. Kevin dubbed it, “Stonehenge.”
One other issue arose today. Anne noted that the slope above the house is fairly steep. She asked about protection from flooding as water cascades down the slope in a heavy rain. (This problem would also affect the pool, as there is a similar slope above it.)
We’re very early in the plan execution…so the earth around the project is chopped up and not at its best.
The earth will be moved as per the agreed-to plan for levels, etc.
There will be some hard landscaping that achieves drainage and in the actual landscape plan any particular drainage issues will be addressed.
So we’ve identified the issue and need to be sure it’s addressed appropriately. We certainly don’t want water pouring through the front door, much less front windows!
Here is the complete photo album from today’s work.
Snow fell over a number of days in mid-January, piling up as high as two meters (6.5 ft) in some villages. (Kevin said there was less in our area, but over 4 feet.)
Then, on January 18, there was a series of four earthquakes in the magnitude range 4.1 – 5.7. These quakes follow the even stronger quakes of last October and August. (There have been more than 45,000 aftershocks since August.)
The biggest catastrophe was in the region just south of Marche, Abruzzo, also hit hard by snow, where the Hotel Rigopiano was buried by an avalanche set off by the quakes and 29 of the 40 people inside died.
The impact on our project is only on timing. Very little work has been or will be able to be completed in January. Kevin reports that the contractor, Francisc, has been able to do some work in his shop, assembling some of the steel needed for the support columns.
I have a lot of things to write about my week in Italy, but I think I’ll start with the earthquakes.
Earthquake Activity This Week
I arrived Monday afternoon and went to Urbisaglia where I stayed in a small, older hotel in the village center until Friday morning. It’s located about where the blue circle is on the map of the quakes that’s on the right of this page.
Wednesday evening about 7:10 pm I was in my room and it shook a little bit. Just a couple of seconds but very noticeable. This one was magnitude 5.5. I figured it was an aftershock to the August 24 quake — rather than being a before-shock for those to come.
About two hours later I was at dinner about 3 miles away, on the bottom floor of a newer (1960s? ’70s?) building and the shaking started again. Everyone bolted for the door, including me, of course. Outside, people were visibly shaken. Some were crying.
The shaking lasted longer this time and was stronger, measuring 6.1. (That difference from 5.5 doesn’t seem that great, but the scale is logarithmic, so this one was roughly 10 times as strong as the first one.)
When I returned to the hotel, the owner came to my room. He reassured me that the hotel was in a building that had been restored to meet earthquake standards.
There were some smaller shocks during the night.
On Friday, I went to the larger town of Macerata. Located where the red circle is, it’s the provincial capital and about 40,000 people, compared to about 3,000 in and around Urbisaglia. Lots of older buildings.
Saturday evening there was a small quake. You could see and hear the television rattle on the table. Magnitude 4.5.
Now the big one. Sunday morning I was just getting up, about 7:40. The room started to shake like crazy. I’m trying to figure out where to go. I’m not dressed, on the fourth floor, with no obvious place to go where the structure might be strongest. I’d say this was 10 seconds of serious fright. Once the shaking stopped, I got dressed, grabbed my stuff, and got to the ground floor and outside. This was a 6.6 quake, so about 30 times stronger than the first one on Wednesday.
Now I had just one problem. The car was in a garage a couple of blocks away and I needed to go back inside to get the keys to get the car.
I didn’t see any visible damage to the buildings nearby, but I wasn’t going to explore. I got the car and drove toward the coast. I wanted out of the hill towns. (My original plan was to go to a sagra delle castagne — a chestnut festival — in a small town in the mountains. It was almost certainly cancelled, but I wasn’t going there to find out.) On the way to my next hotel near the coast and the airport, I decided to stop at IKEA just to what they had that we might use in the house. To my surprise, it was closed, at least for a couple of hours, I assume to check the building.
While this week and year have been very active seismically, history shows this level and severity is very unusual. I found a list of quakes in Italy. In Marche, there have been 9 over 5.0 Here’s the list, with dates, in order of severity.
So the top 3 and number 6 have been this year.
I’m hoping that the pressure on the faults has already released and we may be in for another quiet period. And our house is being built to standards to survive, at least long enough to escape, in an 8.5 or so, and there’s never been a quake nearly that big in Italy.
So the risk we do face is when we are in a village somewhere and there is a 6.0 or over.
I’m now back from my trip and a 4.9 aftershock was recorded today in the same area. Also, scientists are using satellite imagery to assess the quake and the likelihood of future events. Here’s a quote from a BBC story:
There remains the potential for future quakes in Italy’s Apennines region, say scientists who have reviewed the latest satellite maps of the region.The new radar imagery suggests Sunday’s big tremor ruptured a segment of a fault in between sections broken by two other quakes in recent weeks.But the Magnitude 6.6 event has still left the deeper parts of the fault system locked in place. And this unrelieved stress now represents a risk down the line.The researchers are keen to emphasize, however, that predicting precisely when and where a future quake might strike is not possible.”
After the destructive earthquake that leveled Amatrice and the surrounding area this week, we’ve been asked many times if the quake was near our property. Well, it depends on what you’d call “near.”
Amatrice (indicated by the pin) is about 100 km south and a little west of Colmurano (indicated by the star), but the quake was felt throughout Marche. Kevin said his house, near San Ginesio, “rocked several times during that night,” but sustained no damage. (It was built about 10 years ago, following the current building regulations designed to reduce earthquake damage.) He also said that 150 houses in the province of Macerata had already been condemned due to the damage.
Since our property has nothing but a ruin on it right now, I’m assuming we had no damage that will affect us. But since the local authorities are now occupied with property inspections and safety evaluations, we’ll probably be facing some delay in getting our approval to build. (The design itself should be fine, as it was made to meet the latest earthquake safety requirements.)
Having well-constructed buildings is important. As I read, “Earthquakes don’t kill people. Falling buildings kill people.” And tsunamis.
But will we be experiencing future quakes that might affect us? What sort of probabilities are we talking about?
The Fault in Our Ground
A major fault line between the large Eurasian plate and the small Adriatic plate runs down the center of Italy through the Appenini mountain range. There’s also pressure from the large Africa plate in the area. This yields over 1000 earthquakes a year in Italy of various magnitudes, all but a handful small.
Looking at Italy as a whole, the highest risk for dangerous quakes follows that fault. This map shows the area in the mountains near Amatrice in the very dark red, indicating high danger. Our area of Marche is less risky, being in the lightest pink color, but still about the middle for risk.
This closeup map is very interesting, but lacking some key information. It shows a past quake near Macerata big enough to include but of some magnitude less than 5.5, but it doesn’t say when. Also, it estimates the annual risk for an event in our area as about 0.20%, but doesn’t say how big the event needs to be to “count.” That translates to a quake of some significant size (>5.0??) every 500 years.
Or it translates to a probability of 5% in the next 25 years. Compare that to this estimate from the US Geological Survey (USGS): “They concluded that there is a 72 percent probability (or likelihood) of at least one earthquake of magnitude 6.7 or greater striking somewhere in the San Francisco Bay region before 2043.”
I wanted a refresher on both how the scale works and how to translate a magnitude into some meaningful terms.
I was surprised to learn that the USGS hasn’t used the Richter scale since the 1970s. They now use the “moment magnitude scale.” (MMS) It is similar to the Richter scale, both in calculation and in damage assessments.
MMS is measured not on a linear scale but a logarithmic one. In practical terms, this means the differences between the intensity of quakes of similar numbers is a lot more than it seems. For example, a 6.0 quake has 32 times the intensity (energy released) of a 5.0, while a 7.0 has 1000 times the intensity of that 5.0.
Interestingly, the amount of time an earthquake lasts gives a good estimate of its intensity. The quake that struck San Francisco during the 1989 World Series lasted about 15 seconds and measured 6.9. The huge earthquake in Japan in 2011 lasted 4 minutes and was a 9.0. (The highest recorded MMS was in 1960 in Chile: 9.5) Anything over a minute or so is going to be real bad.
The intensity is also linked to the length of the fault line that is displaced. It’s thought that the maximum for a San Andreas quake is about 8.2. That’s big, but small compared to the potential of the Cascadia subduction zone near Seattle: 9.2.
The Amatrice earthquake was measured at 6.2. Here’s a sense of what happens in a 6.0-6.9 quake. It matches this quake fairly well: “Damage to a moderate number of well-built structures in populated areas. Earthquake-resistant structures survive with slight to moderate damage. Poorly designed structures receive moderate to severe damage. Felt in wider areas; up to hundreds of miles/kilometers from the epicenter. Strong to violent shaking in epicentral area.”
Small earthquakes happen all the time. Fortunately. the big ones are rare.