Earthquakes Heatmap

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var blur = document.getElementById('blur');
var radius = document.getElementById('radius');

var vector = new ol.layer.Heatmap({
  source: new ol.source.Vector({
    url: 'https://openlayers.org/en/v4.6.4/examples/data/kml/2012_Earthquakes_Mag5.kml',
    format: new ol.format.KML({
      extractStyles: false
    })
  }),
  blur: parseInt(blur.value, 10),
  radius: parseInt(radius.value, 10)
});

vector.getSource().on('addfeature', function(event) {
  // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
  // standards-violating <magnitude> tag in each Placemark.  We extract it from
  // the Placemark's name instead.
  var name = event.feature.get('name');
  var magnitude = parseFloat(name.substr(2));
  event.feature.set('weight', magnitude - 5);
});

var raster = new ol.layer.Tile({
  source: new ol.source.Stamen({
    layer: 'toner'
  })
});

var map = new ol.Map({
  layers: [raster, vector],
  target: 'map',
  view: new ol.View({
    center: [0, 0],
    zoom: 2
  })
});

blur.addEventListener('input', function() {
  vector.setBlur(parseInt(blur.value, 10));
});

radius.addEventListener('input', function() {
  vector.setRadius(parseInt(radius.value, 10));
});

<!DOCTYPE html>
<html>
  <head>
    <title>Earthquakes Heatmap</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v4.6.4/css/ol.css" type="text/css">
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src=""></script>
    <script src="https://openlayers.org/en/v4.6.4/build/ol.js"></script>
  </head>
  <body>
    <div id="map" class="map"></div>
    <form>
      <label>radius size</label>
      <input id="radius" type="range" min="1" max="50" step="1" value="5"/>
      <label>blur size</label>
      <input id="blur" type="range" min="1" max="50" step="1" value="15"/>
    </form>
    <script>
      var blur = document.getElementById('blur');
      var radius = document.getElementById('radius');

      var vector = new ol.layer.Heatmap({
        source: new ol.source.Vector({
          url: 'https://openlayers.org/en/v4.6.4/examples/data/kml/2012_Earthquakes_Mag5.kml',
          format: new ol.format.KML({
            extractStyles: false
          })
        }),
        blur: parseInt(blur.value, 10),
        radius: parseInt(radius.value, 10)
      });

      vector.getSource().on('addfeature', function(event) {
        // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
        // standards-violating <magnitude> tag in each Placemark.  We extract it from
        // the Placemark's name instead.
        var name = event.feature.get('name');
        var magnitude = parseFloat(name.substr(2));
        event.feature.set('weight', magnitude - 5);
      });

      var raster = new ol.layer.Tile({
        source: new ol.source.Stamen({
          layer: 'toner'
        })
      });

      var map = new ol.Map({
        layers: [raster, vector],
        target: 'map',
        view: new ol.View({
          center: [0, 0],
          zoom: 2
        })
      });


      blur.addEventListener('input', function() {
        vector.setBlur(parseInt(blur.value, 10));
      });

      radius.addEventListener('input', function() {
        vector.setRadius(parseInt(radius.value, 10));
      });
    </script>
  </body>
</html>