var map;

function createMap () {

var options = {

center: { lat: 0, lng: 130 },

mapTypeId: 'terrain',

zoom: 2

};

map = new google.maps.Map(document.getElementById('map'), options);

var script = document.createElement('script');

script.src = 'https://developers.google.com/maps/documentation/javascript/examples/json/earthquake_GeoJSONP.js';

document.getElementsByTagName('head')[0].appendChild(script);

map.data.setStyle(function(feature) {

var magnitude = feature.getProperty('mag');

return {

icon: getEarthquakeCircle(magnitude)

};

});

}

function getEarthquakeCircle (value) {

return {

path: google.maps.SymbolPath.CIRCLE,

fillColor: 'purple',

fillOpacity: .2,

scale: Math.pow(2, value) / 2,

strokeColor: 'white',

strokeWeight: .5

};

}

function eqfeed_callback (geojson) {

map.data.addGeoJson(geojson);

}