def get_gmfs_by_imt(fname, sitecol, imts):
"""
Return a list of dictionaries with a ground motion field per IMT,
one dictionary per rupture.
:param fname: path to the CSV file
:param sitecol: the underlying site collection
:param imts: the IMTs corresponding to the columns in the CSV file
"""
dicts = []
with open(fname) as f:
for row in csv.reader(f):
indices = map(int, row[1].split())
sc = FilteredSiteCollection(indices, sitecol)
dic = AccumDict()
for imt, col in zip(imts, row[2:]):
gmf = numpy.array(map(float, col.split()))
dic[imt] = sc.expand(gmf, 0)
dic.tag = row[0]
dicts.append(dic)
return sorted(dicts, key=lambda dic: dic.tag)
