def get_hcurves(self, imtls=None):
        """
        :param imtls: intensity measure types and levels
        :returns: an array of (R, N) hazard curves
        """
        self.init()
        if imtls is None:
            imtls = self.imtls
        pmaps = [pmap.convert2(imtls, self.sids)
                 for pmap in self.get_pmaps()]
        return numpy.array(pmaps)
:param imtls: intensity measure types and levels
        :returns: an array of (R, N) hazard curves