4 replies to this topic

[Val]

Hello all,

My lab partner and I are doing a map on earthquakes in California for the month of November. We have the earthquake data in Excel and transfered it to ArcMap. We are having trouble with it plotting the points on our base map, its not matching the basemap so the dots are not in California they are in the ocean. Anyone know how to fix this?

[Hans van der Maarel]

My lab partner and I are doing a map on earthquakes in California for the month of November. We have the earthquake data in Excel and transfered it to ArcMap. We are having trouble with it plotting the points on our base map, its not matching the basemap so the dots are not in California they are in the ocean. Anyone know how to fix this?

Sounds like a coordinate system mismatch. You'll need to specify the coordinate system (and projection) used by both, then ArcMap will be able to match them. Didn't you get a warning about that when you imported the points?

Aside from that, keep in mind that it is (at least geologically) possible for earthquakes to happen in the ocean.

[David Medeiros]

As Hans said, its possibly a coordinate system mismatch, meaning you either aded the points with out assigning a coordinate system or assigned the wrong one. Remember that when you import data to a map from excel you initially assign the data the coordinate system it has, not what you want it to be in the map.

If you are confidant that you are assigning the correct coordinate system on import than it may be the values in the table itself. They may be missing a negative value for the longitude. Or, you may have switched the lat for the long on import. Check all of these things and let us know if anything works.

David

[Val]

Thank you! The coordinate systems were not matching. Also I was looking at the data my partner and I have gathered about California earthquake activity and we saw that most of the earthquakes occur in South California, is that because the San Andrea Fault goes through South California more than North California? Thanks.

[David Medeiros]

Thank you! The coordinate systems were not matching. Also I was looking at the data my partner and I have gathered about California earthquake activity and we saw that most of the earthquakes occur in South California, is that because the San Andrea Fault goes through South California more than North California? Thanks.

I think there is a more complex fault system in S CA but that may have nothing to do with the numbers. When looking at only one month of earthquakes you are bound to get a non-representative sample. A better study would be to look at monthly or yearly averages averages over some longer period of time.