week5

The quakes dataset has very thorough documentation, with information being provided even for columns that are self-explanatory (such as time and latitude). With that said, there are multiple columns which are not self-explanatory - including nst, gap, rms, magType, status, and magNst. The meanings of five of these columns are as follows:

• nst - The number of seismic stations used to determine the location of an event

• rms - root mean square residual for observed arrival time of an event vs predicted arrival time

• magType - the method used to determine the event’s magnitude, with a link to a table explaining each possible value

• status - whether an event was reviewed automatically or by a human

• magNst - the number of stations used to determine the event’s magnitude

The data may have been encoded this way as the column names are all closely tied to their meanings while still being single words or short strings of characters instead of multiple words. There are some values within certain columns that are not explained by the documentation, but these have been discussed previously.

I do not think not reading the documentation would have changed much about how I interact with the dataset - even the meanings of the magnitude types could likely have been found elsewhere, though I suspect that searching for them would likely have simply led me to the documentation - as the primary focus of my interactions has been with magnitude, latitude, longitude, and type, all of which are self-explanatory.

The documentation may not adequately describe ‘gap’, though I suspect that people working within the field of seismology or in related fields would likely understand what it is referring to - I suspect this is the reason I found the description inadequate.

In the documentation, ‘gap’ is described as ‘the largest azimuthal gap between azimuthally adjacent stations (in degrees)’, and after some searching, it seems to be the measure of the largest angle of all angles between any two adjacent lines from the seismic event to the seismic stations which detected it (if you ignore any height and distance differences, see images below).

ggplot() + geom_point(aes(x=0, y=0), color = "red", size = 3) + geom_point(aes(x=30, y=0.7)) + geom_point(aes(x=120, y=0.2)) + geom_point(aes(x=140, y=0.5)) + geom_point(aes(x=210, y=0.6)) + geom_point(aes(x=280, y=0.9)) + geom_point(aes(x=360, y=0.4)) + coord_polar() + theme(axis.title.x = element_blank(), axis.text.x = element_blank(), axis.title.y = element_blank(), axis.text.y=element_blank(), axis.ticks.y=element_blank())

ggplot() + geom_segment(aes(x=120,y=1,xend=140,yend=1),linewidth=1) + geom_segment(aes(x=140,y=1,xend=210,yend=1),linewidth=1) + geom_segment(aes(x=210,y=1,xend=280,yend=1),linewidth=1) + geom_segment(aes(x=280,y=1,xend=360,yend=1),linewidth=1) + geom_segment(aes(x=0,y=1,xend=30,yend=1),linewidth=1) + geom_segment(aes(x=30, y=0, xend=30, yend=1),color="blue") + geom_segment(aes(x=120, y=0, xend=120, yend=1),color="blue") + geom_segment(aes(x=140, y=0, xend=140, yend=1)) + geom_segment(aes(x=210, y=0, xend=210, yend=1)) + geom_segment(aes(x=280, y=0, xend=280, yend=1))+ geom_segment(aes(x=0, y=0, xend=0, yend=1)) + geom_point(aes(x=0, y=0), color = "red", size = 3) + geom_point(aes(x=30, y=0.7), color="blue") + geom_point(aes(x=120, y=0.2), color="blue") + geom_point(aes(x=140, y=0.5)) + geom_point(aes(x=210, y=0.6)) + geom_point(aes(x=280, y=0.9)) + geom_point(aes(x=360, y=0.4)) + geom_segment(aes(x=30,y=1,xend=120,yend=1), color="blue",linewidth=1.5) + coord_polar() + theme(axis.title.x = element_blank(), axis.text.x = element_blank(), axis.title.y = element_blank(), axis.text.y=element_blank(), axis.ticks.y=element_blank())

#yes, this is all just for one image

Image 1 shows a hypothetical seismic event (red) detected by 6 stations (black). Image 2 additionally shows the azimuthal gaps between each two adjacent stations (though not their measure), with the maximum azimuthal gap and its associated stations in blue.