Quake-Catcher Network: Using distributed sensors to record earthquakes, to put that data into existing regional seismic networks.
Aim: To better understand earthquakes and mitigate seismic risk by increasing density of seismic observations.
Uses new low-cost sensors that measure acceleration, so can see how much ground shakes during earthquakes. Using BOINC platform. Need volunteers to run sensors, or laptop with sensors.
Why do we need this extra seismic data. Need an idea of what the seismic risk is in an area, look at the major fault systems, population density, and type of buildings.
Where are the faults? Want the sensors in places where earthquakes occur. GSHAP map, shows areas of high seismic risk near plate boundaries. Most concerned with population centres, want sensors where people are, so can get community involved. Looking at cities of over 1m people in areas of high seismic risk.
Construction standards in some areas mean buildings can withstand shaking. But two very large earthquakes took place this year e.g.: Haiti was a bit problem because they have infrequent earthquakes and very low building standards. Chile, had relatively few deaths, and even though some damage, the buildings remained standing.
Seismic risk, look at what happens in the earthquake fault. Simulation of San Andreas fault, shows how much slip, a lot of complexity in a rupture. Very high amplitude in LA basin because it’s very soft sediment which shakes a lot.
Need to figure out how buildings respond. Built 7 storey building on a shake table and shook it, with sensors in and recorded what happened to it. Shake table can’t replicate real earthquakes perfectly. Also have many different types of structure so hard to get the data for them all.
Instead, use sophisticated modelling to understand what happens along the fault, propagation, and building reaction.
Simulations now much more detailed than observed, so no way to check them.
Need to add additional sensors. Seismic stations run upwards of $100k dollars each. Can’t get millions of dollars to put up a sensor net.
Instead use accelerometers that are in laptops, e.g. Apple, ThinkPad, which are used to park hard drive when you drop them. Can tap into that with software in the background to monitor acceleration. Can record if laptop falls off desk or if there’s an earthquake.
External sensors can be plugged into any computer, cost $30 – $100 each, so inexpensive to put into schools, homes etc. Attached by USB.
Location, if you have a laptop you move about, so need laptop by IP, but user can also input their location which is more exact than IP. And user can enter multiple locations, e.g. work, home.
Timing, there’s no GPS clock in most computers, and want to know exaclty when a particular seismic wave arrives, so do network time protocol and pings to find the right time.
Noise, get much more noise in the data than a traditional sensor, e.g. laptop bouncing on a lap. Look at clusters. If one laptop falls on a floor, they can ignore it, but if waves of laptops shake and the waves move at the right speed, they have an event.
Have 1400 participants globally, now trying to intensify network in certain places, e.g. Los Angeles.
Use information for detection of earthquakes, then look at some higher order problems, e.g. earthquake source, wave propagation.
Had one single user in Chile at the time of the earthquake. Software looked at current sensor record and sees if it’s different to previous. Info sent to server after 7 seconds. Soon after earthquake started, internet and power went out, but they did get the date later.
Took new sensors to Chile and distributed them around the area. Put up a webpage asking for volunteers in Chile and got 700 in a week. Had more volunteers than sensors. Had 100 stations installed.
There were many aftershocks, up to M6.7. Don’t often have access to a place with lots of earthquakes happening all at once, so could test data. Looked for aftershock locations, could get them very quickly. Useful for emergency response.
Had stations in the region and some had twice as much shaking as others, gives idea of ground shaking.
Want to have instruments in downtown LA. Have a high-res network in LA already but station density not high enough to look at wave propagation. If put stations in schools, then can get a good network that will show structure of LA basin.
Will also improve understanding of building responses. You can look at dominant frequency that a building shakes at, if that changes then the building has been damaged.
Want to make an earthquake early warning system. An earthquake starts at a given location and the waves propagate out. If you have a station that quickly record the first shaking, and you can get an location and magnitude from that, then because seismic waves travel slower than internet traffic you can get a warning to places further away. More sensors you have, the quicker you can get the warning out.
Working with Southern Californica quake network to see if they can integrate two sensor networks. Also working with Mexico City to install stations, as currently only have a few stations. If any one of them goes down, it affect their ability to respond.