natural_disaster_impact_effect

natural_disaster_impact_effect = {
	scope:situation = {
		switch = {
			trigger = situation_type
			natural_disaster_earthquake = {
				every_situation_county = {
					custom = every_disaster_county_custom
					change_county_control = natural_disaster_earthquake_control_loss_value
					if = {
						limit = { scope:situation.var:severity >= 2.5 }
						add_county_modifier = {
							modifier = tgp_natural_disaster_earthquake_3_county_modifier
							duration_desc = until_the_disaster_is_over
							years = 25
						}
					}
					else_if = {
						limit = { scope:situation.var:severity >= 1.5 }
						add_county_modifier = {
							modifier = tgp_natural_disaster_earthquake_2_county_modifier
							duration_desc = until_the_disaster_is_over
							years = 25
						}
					}
					else = {
						add_county_modifier = {
							modifier = tgp_natural_disaster_earthquake_1_county_modifier
							duration_desc = until_the_disaster_is_over
							years = 25
						}
					}
				}
			}
			natural_disaster_flood = {
				every_situation_county = {
					custom = every_disaster_county_custom
					change_county_control = natural_disaster_flood_control_loss_value
					if = {
						limit = { scope:situation.var:severity >= 2.5 }
						add_county_modifier = {
							modifier = tgp_natural_disaster_flood_3_county_modifier
							duration_desc = until_the_disaster_is_over
							years = 25
						}
					}
					else_if = {
						limit = { scope:situation.var:severity >= 1.5 }
						add_county_modifier = {
							modifier = tgp_natural_disaster_flood_2_county_modifier
							duration_desc = until_the_disaster_is_over
							years = 25
						}
					}
					else = {
						add_county_modifier = {
							modifier = tgp_natural_disaster_flood_1_county_modifier
							duration_desc = until_the_disaster_is_over
							years = 25
						}
					}
				}
			}
		}
	}
}

As written in game/common/scripted_effects/10_dlc_tgp_natural_disaster_scripted_effects.txt.